Impossible to choose from so many options, but here it goes:
Black: Bathory - Under the sign of the black mark
Pagan: Moonsorrow - Suden Uni
NWOBHM: Judas Priest - British Steel
Power: Gamma Ray - Heading for tomorrow
Thrash: Overkill - Ironbound (was going to say Mercyful Fate, but would...
^ speaking of Polish, I've discovered a damn good BM band! They only have one Ep in 2011, so I'm waiting to see what else they come up with...
http://www.youtube.com/watch?v=vVrtxkHWjAg&noredirect=1
Atoma - Skylight 2012, has some beautiful post rock/dark metal songs. Really gets better with every listen ^^
People that like Alcest/ Agalloch/ Anathema/moody stuff should check out this band, they're good!