Rock music, at its core, was a product of the suburbs. Kids saw how fake it was to run away from problems to a boring little world where there was no hope of adventure. They also finally had money, because they were gonna need cars to get around.

Marketers saw this and started selling them country music sped up with black vocal styles, except made white, because the audience was completely white. It’s important to note that rock and blues were a scam. Nothing in them did not pre-exist, but by making some elements of what did exist outlandish, the marketers were able to claim it was new.
...
Metal was a rebellion against this, in that in the midst of the summer of love, Black Sabbath were preparing to unleash something that sounded like a horror movie and had the same dark topicality which wasn’t about any single human. Rock was about the individual escaping by doing the forbidden, but metal was about finding the forbidden, esoteric truth to reality, which is that the individual is frail.
http://metal-blogs.com/death/2007/12...l-versus-rock/

I'd like to see more examples, but I agree. There is something in the spirit of metal (and in prog rock, when it's good) that isn't like regular rock at all. In fact, it's not rock. It's something different, using rock instruments, but if instrumentation was all that mattered, we'd call rock waltzes.