Scorps: German hard prog until Uli left, then straight-arrow party metal
Mercyful Fate: made two of the best metal albums ever
WASP: funny, couple OK songs, mostly stupid (dumb enough to have Metallica open for them in 84)
King Diamond: first LP was pretty good, then went kooky with the Broadway dramatics
Venom: not very good, for some reasons metalically-clueless indie/punkers zoned in on these guys (Sonic Youth , Beasties, etc), true headbangers were puzzled, Slayer were 1000x better
'80s hair metal: mainly started by Motley Crue's Theatre of Pain record, roots in Kiss and Aerosmith, driven by poon, money, and drugs, 100% false metal