Dude, you have no idea how the world gets turned down when you're listening to metal. Strangely, the more "extreme" the metal, the greater the affect.

It's this lovely blend of catharsis, the beat being quasi-hypnotic, and a sense that there is a sea of other metalheads out there moshing to the same thing, and that same thing is often a scathing hatred of the futility of so many human endeavors.

My wife even noticed it, early in our life together. Said basically the same thing as you did, having no clue how I wasn't out there punching kittens and slaying enemies after fifteen minutes of listening. Instead, I throw on something like Dimmu Borgir, Metallica (not all that extreme tbh, but still), or Amon Amarth, and ten minutes later, I'm all chilled the fuck out and the only side effect is a tendency to run around the house growling lyrics at everyone while giggling maniacally.

Okay, so, that last part is a me thing, not really universal to metalheads. Or, not that they'll admit in public. Also, if you've never put on socks so that they flop around at the toes, then gambolled through the house, hopping from foot to foot while screaming "dressed as goblins" for fifteen to twenty minutes, you are a poser. Or sane. Also, nekrogoblikon ftmfw!