I find some Heavy Metal takes me to a greater high than anything else in my life.
For those who've been raised in repressive religious environments it can also be quite liberating to swing the other way, at least for a while...
See what it was that I used to be so afraid of, and laugh.
I do try to maintain some balance though, from sometimes feeling into the Ancient Egyptian styled Deathmetal of 'Nile', another time listening to the sweet female voice and orchestra of 'Within Temptation', etc.
Life is primarily about experience, not just choosing 'either dark or light', I'm never comfortable being too long in any extreme though...
But it's all good, for my mind.
In fact there's more talent, soul and passion in some of these 'fringe' bands than in 99% of music you'll find on the pop charts.
The 'evil' image get's cultivated by some metallers for the 'shock factor' in reaction to christianity, being the dominant religion in western society.
It also then get's reinforced by christians who see this and feel vindicated...
Music does affect your feelings though, but as long as the music is being chosen by you, not your life dictated by the music...
It's all good.