In my experience most metal musicians can hold their own with the best of them when it comes to hard core music nerding with thing like idiosyncratic time signatures and unusual chord and key changes.
Maybe your Berkeley grad metal practitioners like Dream Theater and probably a lot of metal in the last decade or two (since the internet and YouTube) but I imagine a lot of garage metal bands from the 70’s and 80’s were probably just playing/writing by feel and a loose understanding of music theory. I’m sure producers helped bring it all together on the album.
Yea, I think we can roughly split metal into pre-90s and post-90s, with 'modern' metal being a lot musical and precise. Just looking at all the people I know that have been in bands, the more into music theory they are, the more likely they are to be in a metal band.
