Bob Rock first worked with Metallica on The Black Album and later produced St. Anger.
Rock's partnership with the band began with the 1991 self-titled album. He helped guide Metallica toward a more polished and spacious production style while encouraging the musicians to record together and refine their performances.
He remained involved through the Load and Reload era and also produced Garage Inc. When Metallica recorded St. Anger in the early 2000s, Rock temporarily played bass because the band did not yet have an official bassist after Jason Newsted's departure.
This connection can cause confusion with later Metallica producers. Rick Rubin produced Death Magnetic, while Greg Fidelman worked on later projects and anniversary material. Bob Rock's defining album-era association is the run beginning with The Black Album.