Well like all music the songs can convey emotions or have messages that goes especially for metal in my experience metal is just misunderstood by people because they just judge them by their style.
It varies. Most do it for shock value, to aggravate parents. Just like those parents aggravated their parents with Alice Cooper, Black Sabbath and Arthur Brown.
Some really believe in some of the evil that their songs represent.
Some really believe in some of the evil that their songs represent.