There's a lot of overlap between metal and classical music (by which I mean orchestral, symphonic, and chamber, not the specific age). Something about the composition and structure of the music activates similar parts of my brain, and both are excellent to work to.
(Of course, there's only so far you can push this—some metal bands are much closer to pop or jazz, and some classical music is quite distinctively its own thing.)
(Of course, there's only so far you can push this—some metal bands are much closer to pop or jazz, and some classical music is quite distinctively its own thing.)