I have also discovered that there is a category of music called “instrumental heavy metal”, but I have not yet done much exploring there. I found out about it through the web comic author Jeph Jacques (https://questionablecontent.net/), who also has a one-man-band called “Deathmøle”.
In college, I found I could study best by listening to Johan Sebastian Bach pipe organ concertos. But for being productive in a work-type setting, I find that it works better to have more up tempo music whose words I know like the back of my hand.
For the same reason I can't listen to podcasts when working.