Heavy Metal is a music genre, it's abbreviation is "Metal".
New Metal, Power Metal, New Wave of British Heavy Metal, Punk etc. are subgenres.
Slayer is Thrash Metal, ACDC is hard rock and no, the founders of metal are more around Black Sabbath, Deep Purple, Led Zeppelin...
As for that poll:
Metallica is Thrash Metal (Years ago it was Trash Metal... It sounds more like Heavy now)
Iron Maiden is the New Wave of British Heavy Metal (It was Heavy metal...)
Black Sabbath is Early Metal(Heavy To Me)
Judas Priest is a bit special but can also be Early Metal (Heayvy To Me)
Dio is Power Metal (So so)
Megadeth is Thrash Metal
I'm not familiar with Saxon
ACDC is Hard Rock (Some musics are like Heavy...)
Slayer is Thrash Metal
OOOOOOOk Muffindo, I thought that Twisted Sister only sang other ppl's songs,but anyway,looolz.