A Japanese private detective, Shunsaku Ban and his nephew, Kenichi, have arrived in the grand city-state of Metropolis. Metropolis itself lies in an unmentioned country. It can best be described as a plutocracy where a man named Duke Red is the most influential citizen, overshadowing President Boon and Mayor Ryon, the heads of state and government of Metropolis. In Metropolis' heavily industrialised futuristic world, artificial intelligence has advanced a great deal and robots are seen everywhere performing many different tasks. Despite their intelligence, robots do not have any of the rights that are granted to human beings. In order not to infringe upon human rights, they are not allowed to have human names nor to travel between the four Zones which Metropolis is divided in without special permission. Thus they live under Apartheid-like conditions.
In order to protect humans from mischievous-minded robots, the "Marduk", heavily armed vigilantes in red uniforms who destroy robots as they please, patrol the streets of Metropolis. The Marduk was a political party that developed into a vigilante group. It is a public secret that their founder is Duke Red, and that his adopted son, Rock, is a leading figure in the organization.
The private detective and his nephew, along with an assigned robot detective (Nicknamed "Pero" by detective Shunsaku; the robot thought it inappropriate to have a human name, but this was made as a reference to the pet dog Shunsaku had in the Tetsuwan Atom manga by Osamu Tezuka, which was called Pero, a Japanese slang for "lick". The story in which Pero appears can be found in vol.1 of Tetsuwan Atom manga.) Both are looking for a person named Dr. Laughton, who is, among other things, suspected by human rights organizations of human rights violations and the trading of human organs. Little do they know that Duke Red has hired Dr. Laughton to manufacture an extremely intelligent robot in the shape of Duke Red's deceased daughter. The robot is to sit on her customised throne - a supercomputer at the top of the newly built Ziggurat, the mountainous, towering government palace that Duke Red has constructed for the military purposes of reaching the stars and establishing control over the entire Earth. Duke Red, without consulting military leaders, tested the Ziggurat's revolutionary solar superweapon of mass destruction, thus compromising national security. President Boon and other government and military leaders discuss the current situation, and plan to arrest Duke Red for treason once enough resentment builds up against him.
Although Laughton's robot is not quite completed (according to him), Duke Red already looks upon it as his late daughter Tima and has started to reject Rock, an orphan he adopted. Rock is determined to recover his father's affection.
Laughton plans to flee Metropolis once the robot Tima is finished. Rock, upon learning of the robot's intended purpose, shoots and mortally wounds Laughton. He then sets fire to Laughton's laboratory, intending to destroy all traces of Laughton's project, including Tima, who lies dormant in suspended animation.
However, Tima wakes up during the fire and is saved by Kenichi. Dr. Laughton dies shortly after being rescued by Shunsaku but manages to utter a few words regarding a precious notebook of his, which the detective saves from the flames. During their escape from the burning building, Kenichi and Tima fall down a sewage drain and become separated from the detective.
Thus, while the detective searches for his nephew, Kenichi and Tima are at the same time being chased by Rock who is monomaniacal about destroying Tima. Rock's determination to track down and kill Tima lies in the determination to recover his father's love and his belief Duke Red should be the one who sits on the throne at the top of the Ziggurat and not a robot.
It is during this time that Kenichi attempts to teach Tima how to speak and interact with people, mostly explaining to her the concept of "you" and "I" among other basic grammatical concepts.
Escaping from Rock, Tima and Kenichi unexpectedly encounter Atlas, leader of a pro-human resistance group of unemployed laborers who live in poverty below Metropolis' glistening surface. Having lost their jobs to robots, these workers live off of government rations and protest against mechanisation. However, their ration supply is terminated for the Ziggurat celebration, so they plan to take up arms and launch a coup d'état against the Marduks and bring down the Ziggurat, an act symbolically related to the Biblical story of the tower of Babel. The revolution starts when Atlas kills Perro, the robot assisting Kenichi's uncle, and the revolutionaries catch the Marduks off-guard.
As President Boon and the government wait for the right time to arrest Duke Red, the President is betrayed and assassinated by his military supreme commander. Duke Red usurps power and declares martial law. Symbolically, winter comes to Metropolis at this time and covers the city in snow. The uprising is suppressed by the military and upon discovering a dying Atlas, Kenichi, along with Tima, rejoins his uncle. Rock appears, wounding the detective with a bullet wound to the arm and knocking Kenichi unconscious.
Duke Red soon arrives, searching for Rock. As he is about to scold Rock for carrying on an operation without his permission, his view drifts to Tima, and he is taken aback in awe by the fact that she is still alive. Tima then falls back into the hands of Duke Red, who exiles Rock for trying to kill her. Having become so attached to her former companion, Tima writes Kenichi's name all over her room, much to the shock of one of the maids.
Rock bribes a maid in order to interrogate Tima and briefly takes her captive in order to dissect her but is then knocked unconscious by Shunsaku Ban, the detective. He has Tima locate Kenichi (creating a large-scale blackout of the city in the process), finding that he is being held captive in the Ziggurat. As Tima and Shunsaku head for the Ziggurat, Duke Red tracks the pair down and captures them both.
Kenichi is reunited with his uncle who declares the mistreatment of his nephew as a direct violation of international law. Tima asks Duke Red if she is a robot or a human, and Duke Red replies that she is a superhuman who has a true destiny: to merge with the Ziggurat and rule the Earth. The detective reveals Dr. Laughton's notebook which contains evidence about Tima and the Ziggurat against Duke Red. It explains that upon merging with the throne, Tima's emotions and memories will be erased in order that she can be the control device used for Duke Red's superweapon.
Suddenly Rock, disguised as a maid, sneaks in and shoots her, only to be shot by one of the guards. When Tima sees the wound she realizes that she is an "artificial human" created to conquer. Angered at how she has been misused, she assimilates with the Ziggurat, only to declare herself the architect of a robot revolution. Taking her seat upon the throne, Tima seizes control of the fortress and orders a biological and nuclear attack on all major cities in the world, intended to annihilate humanity.
The robots begin the attack against humanity, and when Kenichi pulls Tima from her throne (at the cost of half her body and clothing deformed by the throne's electromagnetic effects), he tries to redeem her even though she repeatedly tries to kill him. The robots kill the Ziggurat scientists and attempt to kill Duke Red, but Rock, who does not want his father killed by machines, presses a button that activates the Ziggurat's superweapon. Upon activation, the Ziggurat begins to explode due to Tima overloading its systems when she integrated herself into the throne and took control of the Ziggurat. The Ziggurat's systems cannot take the activation of the weapon, so it overloads beyond its limits and is destroyed, along with the surrounding area of Metropolis and its four Zones.
Kenichi continues to try and redeem Tima, who in turn tries to kill him. Tima grabs Kenichi by the neck and as she does so, her CPU overloads and deactivates, causing her to become disoriented and lunge over the walkway's edge, taking Kenichi with her. As he falls, Kenchi manages to grab onto a lower walkway and pull himself up. On regaining his balance, he spots Tima dangling hundreds of metres above the ground, with only a wire, connected to her hand, keeping her from falling. The other end is attached to a piece of the throne that came away when Kenichi pulled her from it, and it is stuck between two girders with Tima in the middle. After her command CPU is deactivated, Kenichi begins to pull her up, and as he does the wire begins to fray. It snaps, but Kenichi grabs Tima's hand, and pleads to her to grab his. As she dangles, she remembers Kenichi's earlier teachings and what he taught her about grammar. Kenichi tries to save the now "redeemed" Tima but fails. Her final words to him are "Kenichi! Who am I?" and she falls to her death as the main section of the Ziggurat is completely destroyed by the nuclear meltdown and explosive destruction.
The next morning, Metropolis lies in ruins and a few robots survive, while human survivors, including Kenichi's uncle, evacuate in an airship. Kenichi stays in Metropolis to find Tima and help the robot survivors. He is surprised to see that several robot workers have recovered Tima's shoes and a few of her parts and proceeds to look for more of her parts in order to rebuild her. Others can interpret this action as though Kenichi is paying his last respects to Tima; after all, she was the most complex robot in the world and would not easily be rebuilt. Later, after a radio finishes playing music, it plays Tima's voice saying: "Who am I?" Since her thoughts are picked up on the radio, this could signal that she is alive somewhere.
Tima (Yuka Imoto/Rebecca Forstadt) — A robot modeled and named after Duke Red's deceased daughter. She is unique in that she appears and looks human, a trait that no other robot shares. However, after she is activated, she has no memory or knowledge about who or what she is. With the help of Kenichi, she hopes to be able to find the answers to these questions. Unfortunately for her, the answers she finds are not very pleasant.
Duke Red (Tarō Ishida/Jamieson K. Price) — The villain of the story and the plutocrat who founded the Marduk, an organization with which he secretly hopes to take over Metropolis. He builds the Ziggurat with claims that it will be a modern masterpiece for the city of Metropolis. However, the Ziggurat is actually a massive weapon with which he intends to use for world domination. As part of his plan, he hopes that Tima, a robotic duplicate of his deceased daughter, will control the Ziggurat and follow along with his master plan.
Shunsaku Ban (Kōsei Tomita/Tony Pope) — A Japanese private detective who has come to Metropolis with a warrant for Dr. Laughton. He is accompanied to Metropolis by his nephew, Kenichi, and is assigned a robot assistant by Superintendent Notarlin. While he appears clumsy and somewhat carefree, he is actually a brilliant detective and knows more about what is going on around him than he lets on. He spends a good portion of the movie searching for Kenichi when they get separated at Laughton's laboratory.
Rock (Kōki Okada/Michael Reisz) — The antagonist and tragic anti-hero of the story. An orphan, he was adopted by Duke Red to help fill the empty void of Duke Red's broken heart when his only child, Tima, died. However, with the notion that Tima can be brought back by building a robotic duplicate, Duke Red has since refused to acknowledge Rock as his son or return his love. Obsessed with regaining his father's affection and infuriated that Duke Red wants to give a robot the "throne" of the Ziggurat, Rock intends to kill Tima so that Duke Red will sit on the throne instead. However, his assassination attempts are foiled by Kenichi who protects Tima. Driven by his need to be accepted by Duke Red, Rock is willing to murder anyone that gets in his way. (While Rock did not feature in the original manga, Duke Red's comments about adopting him after "the last war" allude to another Tezuka manga from the same period, Nextworld, although this manga was actually released after Metropolis.)
Makeru Butamo as Dr. Laughton (Junpei Takiguchi/Simon Prescott) — A mad scientist who is on the run from the law for his illegal experiments and the charge of human organ trafficking. A scientific genius, he is commissioned by Duke Red to build Tima in a secret lab within Metropolis. However, Dr. Laughton has other ideas and doesn't want to hand his greatest creation over to Duke Red. When Rock finds his lab, he shoots Laughton and attempts to destroy everything in the lab. Trapped in the burning wreckage, Dr. Laughton is found by Detective Shunsaku Ban right before he dies.
Notaarin as Superintendent Notarlin (Shun Yashiro/William Knight) - Superintendent of the Metropolis police force, Superintendent Notarlin spends most of his time handling paperwork behind his desk in the police department. When Shunsaku Ban and Kenichi come to him with their request for the Metropolis Police's cooperation in apprehending Dr. Laughton, he unfortunately is only able to give them a robotic assistant. With the recent activity in Metropolis, he can't spare any officers to Detective Ban's search. He simply gives them the paperwork needed to be assigned a trench-coat wearing robot to guide them around Metropolis. In the original manga, Notarlin has a much larger role, serving as a rival/comic foil to Duke Red, a role which he would later reprise in several other Tezuka manga featuring both characters including Nextworld. His name is a play on the Japanese word "No-tarin" which means stupid, or literally translated "lacks brain".
Pero (Norio Wakamoto/Dave Mallow) - A robot assigned to Shunsaku Ban by Superintendent Notarlin to aid in his investigation. Amazed at the advanced technology of Metropolis, Shunsaku Ban often asks the robot questions to try and understand him a bit better. However, as robot protocol forbids him to have a human name, Shunsaku Ban addressed him as "Pero" instead of his more formal identification number 803-D-RP-DM-497-3-C. (He accepts this name as it is a name more associated for pets and not humans) He eventually makes a brave sacrifice for Shunsaku Ban later in the movie. Pero first appeared in the Astroboy manga story "The Hot Dog Corps" as a cyborg created from a dog of the same name that was once owned by Ban.
Ham And Egg as Himself (Masashi Ebara/Robert Axelrod) - Ham Egg is a police officer who guards the entrance to Zone 3, a section of Metropolis that is used for power production. Entrance to Zone 3 is restricted to robots and authorized personnel only due to its dangerous factory-like atmosphere. However, when Rock insists that he gain entrance to Zone 3, Ham Egg escorts him in personally. When he witnesses Rock's attempt to assassinate Tima, he tries to stop him, only to be shot and killed intentionally by Rock.
Atlas as Himself (Norihiro Inoue/Scott Weinger) - The leader of resentful unemployed labourers who reside in the slums of Zone 1. He and his rebel organization have a strong hatred for robots, blaming them for putting them out of work. Since Duke Red and his companies are primarily responsible for the construction and manufacturing of most, if not all, robots, Atlas hopes to lead his group to victory in displacing Duke Red and restoring jobs to the people and not the robots. Note that this Atlas has little to nothing to do with the Atlas of Astroboy, although his distinctive dreadlocks appear to have been inspired by the original manga Atlas' bizarre "headplugs".
Boon Marukubi as President Boone (Masaru Ikeda/Richard Plantagenet as "Steve McGowan")
Skunk Kusai as General Skunk (Toshio Furukawa/Dan Woren) - A military general who is in charge of the Metropolis army. While he appears to be loyal to President Boone, he is secretly working for Duke Red and the Marduk. When Duke Red begins the Coup to overthrow President Boone, Skunk shoots and kills Acetylene Lamp when he tries to stop Duke Red. After killing him, Skunk envisions a future of war and destruction, showing that his deepest desire is constant and everlasting war and death.
Dr. Ponkotsu (Takeshi Aono/Doug Stone) - A scientist that works within the Ziggurat and monitors its functions and operations. He is responsible for the testing and working functions of the weapon that is the true Ziggurat, and reports directly to Duke Red. Dr. Ponkotsu also knows that the weapon can not be fully controlled unless Tima is able to take the "throne". He originally appeared in the same Astroboy story as Pero.
Enmy (Mami Koyama/Barbara Goodson) - A maid within Duke Red's home who is assigned the task of watching over Tima when Duke Red finds her and discovers that she is still alive. While disturbed at Tima's obsession of finding this "Kenichi", she tricks Tima into meeting a disbarred Rock after he bribes her to bring Tima to him. Like Notarlin, Emmy is also a major character from the manga who only has a brief cameo in the anime version.
However, this cinematic adaptation of Tezuka's story integrates far more elements from the Fritz Lang film Metropolis. When making the original Metropolis manga, Tezuka said that the only real inspiration he got from Fritz Lang's Metropolis was a still image from the movie where a female robot was being born. In addition to adopting set designs of the original film, this version introduces a strong and pervasive theme of class struggle in a dystopian, plutocratic society and expands it to examine the relationship of robots with their human masters. (This relationship was explored by Tezuka in great detail with his popular series Astro Boy.) The film adaptation also removes many of the more fanciful elements out of Tezuka's manga, such as a flying, gender swapping humanoid. Here, Mitchi is replaced with "Tima", who is permanently female and cannot fly.
The Japanese release of the film shows a picture after the credits depicting a shop named "Kenichi & Tima Robot Company," with Tima visible in the window (or possibly driving the truck as the person looks similar to Tima). This could imply that Kenichi succeeded in rebuilding Tima (even though it would be unclear whether he had managed to reactivate her), or the Tima in the window could only be a painting or picture. This picture was included in the English Theatrical release of the film, however was not present on the DVD release for unknown reasons.