Jason Curtis Newsted was born March 3, 1963, in Battle Creek, Michigan. His European ancestors were Germans from Baden. Jason went to Gull Lake High School in Richland, Michigan, joining Arizona thrashers Flotsam and Jetsam in 1982. Jason left them to join Metallica in 1986. after the tragic death of popular bassist Cliff Burton. Following auditions and an evening of drinking, the three members of Metallica, James Hetfield, lead guitarist Kirk Hammett, and drummer Lars Ulrich, reportedly came to a decision in the restroom of "Tommy's Joynt" in San Francisco amid the urinals, and upon their return to the bar asked Jason to join Metallica. It was Ulrich who asked Newsted coolly: "Want a job?" Jason's first show with Metallica was in Reseda, California, on November 8, 1986.

After confirming Jason as their new bassist (becoming Metallica's longest serving bassist) Metallica constructed a cheap studio in Ulrich's garage in order to acclimatise Jason to Metallica. In this studio, the band quickly recorded an album consisting completely of cover songs called The $5.98 EP: Garage Days Re-Revisited, a homage to the New Wave of British Heavy Metal bands that influenced them. Jason was often referred to by the nickname "Jason Newkid" and in autograph sessions Jason would sign his name and add "Bassface" below, often having the B marked out by one of the other band members.

In 1988, the band recorded ...And Justice for All, Jason's official debut with Metallica. While the album contains classic Metallica songs such as "Blackened" (which Jason co-wrote), "One", and "Harvester of Sorrow", the bass guitar is all but non-existent, buried under layer upon layer of rhythm guitar tracks. Only a trained ear can make out many of the parts, although this can also be partially attributed to Jason's doubling of Hetfield's rhythm guitar parts (drummer Ulrich has challenged fans to find any instance in any song on the album in which Jason is not doubling the rhythm parts).

Jason withstood an ongoing series of practical jokes during the year-long Damaged Justice tour supporting ... Justice .... Some of his hazing experiences would include: being tricked into eating wasabi, the band members ordering alcoholic drinks and charging it to his hotel room and, mentioned during the 2001 Playboy interview, having his personal belongings thrown out of his hotel window. He said the hazing went from fraternity pranks (such as the autograph sessions mentioned above) to being downright cruel. He felt that the hazing never stopped. Many fans who have come to his defence have cited this behaviour among the evidence that he was never fully accepted as an equal member of the band. As a running gag with Jason, James Hetfield would ask the crowd during live performances what should be played next, and Jason would suggest, "Something with Satan In It". Of course, James Hetfield would ignore Jason and the rest of the band would criticize him humorously (as seen on the Seattle disc of Metallica's Live Shit: Binge & Purge).

He left Metallica in January 2001 and joined the Canadian metal band Voivod in 2002. The last song Jason played with Metallica was Fade to Black at the VH1 Music Awards and he knew at the time that it was going to be the last song he would play with the band. During the bridge, when Hetfield sings, "death greets me warm, now I will just say, goodbye," Jason can be seen waving to the camera at that moment before playing the last few minutes of the song.

In the film Some Kind of Monster, Newsted claimed that he left Metallica because of James Hetfield's controlling desire to keep everyone in Metallica and out of side projects, specifically Echobrain, which Newsted desired to release an album and tour with. (Kirk Hammett is credited with playing a guest solo on one track, "Suckerpunch.") Jason also admitted that after 15 years, he still felt that his bandmates had not accepted him as an equal to his predecessor, Cliff Burton. He also said that the band's decision to hire a psychologist was, "Really fucking lame. And weak."

In 2003, Metallica picked former Ozzy Osbourne and Suicidal Tendencies bassist Robert Trujillo as Newsted's replacement. Jason was very happy with the decision Metallica made and in a bizarre twist, Ozzy immediately chose Jason to replace Rob for Ozzfest 2003. Following the end of Ozzfest, Jason left Ozzy's band to concentrate on his work with Voivod. Even though he isn't 100% happy with his relationship with Metallica, they are on better terms than they were immediately after his departure. He has said, "I'll be right there [at the concerts] cheering them on" on MTV Icon. However, after finding out the line up for the Summer Sanitarium Tour 2003, Newsted criticized Metallica for touring with nu-metal bands such as Linkin Park and Limp Bizkit, stating that they were only doing that to get stadiums full. He also noted that he wasn't saying that to offend his erstwhile bandmates, but simply as a concerned fan. He briefly criticized the production of post-Newsted album St. Anger as well, to which Hetfield has responded that "he's just a voice among many."

In July 2006, Jason Newsted joined Mötley Crüe drummer Tommy Lee and former