As an entire album, I think Master of Puppets is one of the best Metal albums ever made. Now many die hard Metallica fans will argue and say Ride The Lighting and Kill Em All is better... But musically speaking ..they matured a whole lot on Master.
I actually saw Metallica 5th row for the Black Album tour...Great concert!
That album was also the last Metallica album for me. Amazing that was in 1991.