IMO, you should check out this link
www.brutalmetal.com
http://www.nwobhm.com/
there's lots of info on this page and you can check out tons of bands.
There's a big A-Z on all kinds of different styles and such and it could
point you in the right direction. The british overall were very influential
in the birth and early years of Heavy Metal. American Rock wasnt doing
a whole lot for Heavy Metal in the 70's and 80's. Van Halen, yes.
Aerosmith, maybe. Nugent, not really. REO Speedwagon, Kansas, Skynyrd,
Allmans, Montrose, Boston - not really. All the big action was in England
with Priest, Maiden, Zeppelin and the New Wave of British Heavy Metal
and all those bands that Metallica always talked about like Def Leppard,
Tygers of Pan Tang, Def Leppard, Angel Witch, Venom, Sweet, Sweet
Savage, Diamond Head, Rainbow, Deep Purple, UFO, Saxon, etc...
Ammended...
And the germans had bands like Scorpions (since 72) and Warlock (lke 84)
and Helloween (like 85) and the Swedes had Hellhammer which became
Celtic Frost later....