I am always so peaceful when listening to heavy metal ... :D

I think the article should focus more on good music elements versus bad music elements. My brain gets annoyed at bad music. Good music can be useful though, in particular for relaxing. I normally dislike jazz-elements, but Sade for instance is acceptable (not pure jazz, but she uses jazzy elements).

Heavy metal/hardcore is good music. Mumble rap is bad music.

Good music is subjective. Aside from the guitar skills involved in shredding, I think heavy metal is probably the worst genre of music.