You stated that Heavy Metal does not fit the WoW aesthetic, therefore we are addressing your concerns about Heavy Metal. If you wish to proclaim other music genres do not fit WoW, then I'd just as easily argue in their defense, on a case-by-case scenario.
Again, I'm holding you accountable for your claims. I'm not sure why you are trying to tangent away to this being about other genres of music; you said the Heavy Metal aesthetic does not fit WoW, therefore we are specifically talking about Heavy Metal.
The game also has Polka music (Brewfest), Asian style Chinese music, African style Drum beats, etc. If anyone made a statement that 'Polka doesn't fit the Warcraft aesthetic' then I would disagree, and I would present examples to support my argument that it's a bogus statement, considering we HAVE Polka music and plenty of Polka references in WoW.