Any Led Zeppellin album, especially one of the first 4.
While they are some of the greatest albums ever made, they are not really metal. I'd go with some classic Black Sabbath if you don't already own them. Judas Priest had some classics and just remastered a couple as well. Iron Maiden? If you don't have any of the first 4 Metallica albums, they are a must as well as Pantera's Cowboys From Hell or Vulgar Display of Power. They are favorites of mine though. I'm not into the death metal screaming/growling kinda stuff.
