Bob Rock produced Metallica's 1991 album, commonly called The Black Album. He shared production credit with James Hetfield, Lars Ulrich, and Metallica, but Rock was the album's principal outside producer.
Metallica hired Rock after admiring his work on Mötley Crüe's 1989 album Dr. Feelgood. The band initially hesitated about working with him, but ultimately believed his approach could help them make their strongest record.
Rock pushed the musicians to record more collaboratively and encouraged live-feeling performances, harmonic vocals, and a louder, clearer bass sound. The demanding sessions created frequent arguments, and the recording process became a major part of later documentaries about the album. A common mix-up is confusing Rock with Flemming Rasmussen, who produced Metallica's earlier albums Ride the Lightning and Master of Puppets.