WAY too tough for me to only pick one, so I had to go with 2 for most of them.
Progressive Metal: Dream Theater - Images and Words, Queensryche - Operation:Mindcrime
Traditional/"Classic" Metal: Black Sabbath - Heaven and Hell, Iron Maiden - Powerslave
Power Metal: Blind Guardian - Imaginations From the Other Side
Speed Metal: Riot - Thundersteel
"Hair" Metal: Whitesnake - Whitesnake
Thrash Metal: Overkill - Horrorscope