Prior to joining Megadeth, he formed and played lead guitar in several other bands, including Deuce, Hawaii, Vixen (not the all-female band of the same name), and notably Cacophony. Cacophony featured neoclassical metal elements and synchronized twin guitar harmonies and counterpoints shared with guitarist Jason Becker on their two albums, Go Off! and Speed Metal Symphony.
Friedman speaks fluent Japanese. He became a regular member of the cast of TXN's musical TV program hebimeta-san (ヘビメタさん) (anglicized as "Mr. Heavy-Metal") with Japanese idol Yoko Kumada before the show came to an end in 2005. He had his own heavy metal TV program called Rock Fujiyama alongside Shelly, Kenny Guy, Rock Ninja Yorimasa and ex-Scanch member, Rolly Teranishi from April 2006 until March 2007. In November~December 2005 he went touring with Japanese singer Ami Suzuki inside her "Suzuki Ami Around the World" Live House Tour, which took place in cities like Tokyo, Osaka and Nagoya.
More recently, Marty has been featured in Jukebox, a television program in which Marty and two Japanese people translate the lyrics of various English songs into understandable Japanese.
In 2005, Friedman appeared on the soundtrack of the video game Heavy Metal Thunder adapted from the hebimeta-san TV show.
Friedman's album, Loudspeaker, was released in Japan on June 26, 2006. It entered the Japanese national chart at #33. This marks the first Top 40 chart position for any of his solo albums.
Marty's "Exhibit A-Live in Europe" CD and "Exhibit B-Live" in Tokyo DVD were released simultaneously in Japan on 8/22 by Avex. The CD and DVD feature different setlists, but with the same band members, Jeremy Colson, Ron Jarzombek and Chris Catero. The artwork was designed by legendary graphic artist Noritaka Sakai, who is responsible for Queen's most successful Japanese editions.
Marty has collaborated with Mutsuhiko Izumi, a video game composer known for his contributions to Konami's Guitar Freaks & DrumMania series to produce "MODEL DD8", and "LIBERTY", two songs featured on Izumi's album "HEAVEN INSIDE." A shorter version of "MODEL DD8" has appeared as the Premium Encore stage of the latest installment of the Guitar Freaks & DrumMania series, "Guitar Freaks V4 & DrumMania V4 Rock×Rock" as of October 28, 2007 in the e-Amusement network.
Marty also has contributed his voice to a character on the Cartoon Network Adult Swim show Metalocalypse.
Marty has composed a song Kirei na Senritsu for the anime Maria-sama ga Miteru which was sung by KOTOKO in 2007.
Also in 2007, Marty appeared on the track "Call Me Evil" on the debut album, Living a Sick Dream by Phoenix, Arizona Metal band Age of Evil.
On March 12th 2008, his eighth solo album, "Future Addict", was released in Japan. The album features reworked, reconstructed, and remade versions of some of Friedman's past songs from his career, as well as three new songs.
When Marty joined Megadeth in 1989, he switched over from Carvin to Jackson Guitars. Primarily, he was responsible for popularizing the now highly acclaimed Jackson Kelly guitar, a sleeker and faster version of the Gibson Explorer Z style shape. The first line of KE1s, which were his signature models, had alder bodies with maple neck through construction and a single Seymour Duncan JB pickup as well as a Kahler Fine-tuning fixed bridge. Later versions of the KE1 would have a Floyd Rose double locking tremolo in place of the Kahler.
Marty used Jackson guitars up until 2000, when the company was bought out by Fender Musical Instruments Corporation. Since 2000, Marty has endorsed Ibanez guitars. He has produced a signature model with Ibanez (based on the Ibanez SZ line of guitars), but this model is as of now only available in Japan and not in the US.
It is hotly contested what amplifiers Marty first used with Megadeth on their landmark album "Rust in Peace." He almost definitely used a Bogner Triple Giant and a Tube Works solid-state preamp for solos, along with a VHT 2150 power amp. Contrary to popular belief the Bogner Fish, which is often cited as the preamp for the album, was first released one year after the album debuted, therefore making it impossible to be the preamp of use on this album. Marty and Dave Mustaine both used Custom Audio Electronics 3+ Preamps and VHT 2150 power amps on the commercially successful "Countdown to Extinction" and "Youthanasia" albums. When recording started on "Cryptic Writings, Marty switched to Crate Amplifiers. He used these on all of his recordings after Youthanasia, primarily using Crate's highly successful Blue Voodoo tube amplifiers. As of 2007 however, Crate has discontinued the Blue Voodoo and Marty now uses ENGL amplifiers. He uses Special Edition heads and Vintage cabinets from ENGL.
| Date of Release | Title | Label |
| September 24, 1990 | Rust in Peace | Capitol Records |
| July 14, 1992 | Countdown to Extinction | Capitol Records |
| October 31, 1994 | Youthanasia | Capitol Records |
| July 18, 1995 | Hidden Treasures (EP) | Capitol Records |
| June 17, 1997 | Cryptic Writings | Capitol Records |
| November 1998 | Cryptic Sounds - No Voices in Your Head (EP) | Capitol Records |
| August 31, 1999 | Risk | Capitol Records |
| Date of Release | Title | Label |
| 1988 | Dragon's Kiss | Shrapnel Records |
| 1992 | Scenes | Shrapnel Records |
| 1995 | Introduction | Shrapnel Records |
| 1996 | True Obsessions | Shrapnel Records |
| 2003 | Music For Speeding | MF Music |
| 2006 | Loudspeaker | Avex Trax |
| 2008 | Future Addict | Avex Trax |