:guitar:
The lyrics DO matter, as does the overall effect on the soul by the tone, rhythm, beat, harmonony, etc. "Megadeath?" Shouldn't the name of this group tell you whose side they are on? Our Lord brings life, Satan, death.
If a person was raised with this sort of music, maybe was exposed to it in the womb, he probably finds it "normal." But that doesn't mean once he is enlightened, that he shouldn't seek to expand his musical horizons to find a genre pleasing to God.
If you like loud and lively, there is plenty of music that fits this description whose purpose is not to pay homage to the devil. Explore the folk music of the world. Giving up heavy metal doesn't mean you must listen only to classical! You will have to look for it, though. What better use for the internet?
Even though Lent is nearly over, try abstaining from heavy metal by replacing it for a month. (Or if too long, a week, a few days!). See if your overall mood, attitude, and spiritual life don't improve! It could be you don't know the difference because you've known nothing else.