Music genres - how much is it about the choice of instruments, vocalists gimmicks and appearance, versus differences in actual melody?

Is dance music performed a few times faster, a few octaves lower, on distorted guitars, double bass, using growling still dance music? Or is it metal? Is this metal? Or this? I'm sure if played during a metal concert it would be considered metal, if the melody wasn't so well known already, of course. Is there anything inherent in melody that makes it a specific genre?