Bob Rock produced Metallica's 1991 Black Album.
Rock was known for his work with major hard-rock and metal acts, and Metallica had been impressed by his production on Mötley Crüe's Dr. Feelgood. His approach encouraged the band to record more collaboratively and to pursue a tighter, more polished sound.
The sessions were not easy. Rock pushed the musicians to reconsider their performances and lyrics, while the band was accustomed to exercising considerable control over its recordings. Arguments and repeated takes became part of the album's difficult production process.
James Hetfield and Lars Ulrich also received assistant-production credits. Rock later worked with Metallica again on subsequent releases, including Load, Reload, St. Anger, Death Magnetic, and Hardwired... to Self-Destruct, although the band's production arrangements changed over time.