Bob Rock had previously worked on Mötley Crüe’s Dr. Feelgood before producing Metallica’s The Black Album.
Dr. Feelgood was released in 1989 and was a major success for Mötley Crüe. Metallica admired Rock’s production work on that record and decided he could help them make a more powerful and focused album. His appointment represented a change from the producers associated with Metallica’s earlier records.
Rock’s influence was not limited to microphone placement or mixing. He encouraged the band to record together more often, emphasized a stronger rhythm section, and pushed James Hetfield toward more developed lyrics and vocal performances. He also helped bring Jason Newsted’s bass into the finished sound more clearly than on …And Justice for All.
The relationship was difficult, especially because Metallica’s members were perfectionists and Rock insisted on many takes. Nevertheless, the partnership produced a record that moved the band from an underground thrash audience to worldwide mainstream success.