In 1989's Legend mini-series, Metron confides in Darkseid about the Anti-Life Equation. Apparently, Metron holds the key to the Anti-Life Equation, however he is a seeker of knowledge and so will tell no one of his knowledge. In a 1983 DC/Marvel crossover, X-Men / Teen Titans, Metron tells Darkseid that Dark Phoenix is a part of the Anti-Life Equation. Recently in the "Death of the New Gods" miniseries the Source explain the origin of the Anti-Life Equation to Metron.
Metron helped contact most of Earth's superheroes in order to gather them during the Zero Hour crisis.
He observed the events of Kurt Busiek's JLA/Avengers comic, giving Iron Man a Mother Box to balance the power given to the Justice League by Grandmaster. His main role during the miniseries was to observe and investigate Krona's actions, refusing to deviate from his non-involvement at the end when Krona demanded his aid. At the end, Metron kept guard over the newly formed Cosmic Egg.
In the 2005 Mister Miracle miniseries, Metron contacts Shilo Norman (the current Mister Miracle) during a stunt gone wrong, making him aware of the Fourth World. In his first appearance in the book, he looks like he has before, but later he disguises himself as an epileptic man in a wheelchair.
During the events of Death of the New Gods, where the mysterious deaths of the entire Fourth World accelerated, Metron tracked and discovered the mastermind: the Source itself, which has in truth been lurking in the backgrounds for millennia trying to reacquire its original powers and reunite with its other half: the Anti-Life Entity. In true form, Metron sought not to stop the Source, but rather to stand by the Source's side and watch & learn as the Fourth World of the New Gods came to an end.
Eventually, after the death of Mister Miracle at the hands of the Source, Metron grows disgusted, and demands his own death. The Source complies, and kills Metron before going to confront Darkseid.
On the first page of Final Crisis #1, an all silver being appears to Anthro the First Boy and proclaims, "I am Metron." later in the issue, Doctor Light and Mirror Master are sent by Libra to recover a device that resembles Metron's chair.
Metron appeared in the final two episodes of Justice League Unlimited. In it, he tries to warn Lex Luthor not to go through with his plan of resurrecting Brainiac, claiming what he will do will affect the universe, but Luthor ignores him and, unfortunately, resurrects a Brainiac-enhanced Darkseid. However, he later provides Luthor with the means to defeat him. He is voiced by Daniel Dae Kim.