Which producer's 1989 album impressed Metallica enough to hire him for The Black Album?

Bob Rock's production of Mötley Crüe's Dr. Feelgood impressed Metallica enough for the band to hire him for The Black Album.

Dr. Feelgood was released in 1989 and became Mötley Crüe's fifth studio album. Metallica admired Rock's production work and believed he could help them make their strongest record, even though the band initially had reservations about changing producers.

Rock brought a different studio philosophy to Metallica. He encouraged the members to record more as a unit, emphasized a live feel, and challenged the band over vocal harmonies and lyrics. The process became difficult and argumentative, but it also helped create a cleaner and more forceful album sound.

The answer is Bob Rock rather than Andy Wallace, whose name is associated with mixing the album. Flemming Rasmussen produced several earlier Metallica albums, including Master of Puppets and ...And Justice for All.