It hurts me to think of all the great metal you'd miss out on if you limit yourself to clean vocals. I'm sure you'll get a decent amount of qualifying recommendations, but if you want to open the floodgates, give the less-accessible vocals another try.
Maybe start off with some
Opeth (alternates between growl and clean).
If you want to broaden your musical horizons, you may need to venture out into the unknown
