Jason Newsted is the bassist credited as a band member on Metallica's 1991 album Metallica, known as The Black Album.
Newsted joined Metallica in 1986 after the death of bassist Cliff Burton and had already appeared on ...And Justice for All. The Black Album was therefore his second Metallica studio album and the first to give his playing a prominent, more audible role in the finished mix. That change was especially noticeable because the bass had been famously subdued on the previous studio record.
The album's core lineup was James Hetfield on vocals and rhythm guitar, Lars Ulrich on drums, Kirk Hammett on lead guitar, and Newsted on bass. This four-member lineup remained intact through the recording and the tour supporting the album.
Newsted left Metallica in 2001, before the recording of St. Anger. Bob Rock played bass on that album, while Robert Trujillo joined the band afterward. Those later lineup changes are why listeners sometimes attach Trujillo's name to Metallica's catalog, but Newsted is the correct bassist for The Black Album.