which metals are considered to be transition metals?
They aren't even Metal. They can be considered Nu Metal or Alternative Metal but its not a form of Death Metal or even True Metal.
You have not done 1 of 2 things You haven't listened to System of a Down, or you haven't listened to Death Metal. Either way the answer is definitely NO! Your girlfriend is 10000% correct. Go and listen to some Norwegian Black Death Metal then you will see the difference.
I'd just call them metal. They're not dark enough for death metal at all. I do like System of a Down.
Heavy Metal or Hard Rock hardly death metal
