People with a theoretical knowledge of Metal they really like to show to everyone that exceeds knowing simple facts, for example that screamo isn"t a genre, but only how scene people call genres like Hardcore, Metalcore, Melodic Death Metal,...., by far, but no idea what being a metalhead means. Some of them haven"t been to a concert in their entire life. They normally have nothing better to do than sitting in front of their computers all day long, watching youtube videos and, by commenting, defending their selection of favourite bands as "the only real Metal" against others and attacking their selections as "not Metal at all", or searching for probably not useful, but scientifically correct genre names. They normally attack people with different opinions personally
(comments under a Messhuggah video)
real metalhead: awesome song! Especially live!!!!!
youtube metalhead 1: nice Progressive Metal
youtube metalhead 2: you retard, are you deaf or what? That"s nowhere near Progressive Metal, it"s Experimental Death Metal!
youtube metalhead 3: you idiot, you"re too stupid for listening! That has no Death Metal elements!!! It"s Technical Post Thrash Metal!!!!!