I never used to like growling or screaming until someone introduced me to In Flames, and the music was incredible and didn't care about the lyrics. From there I moved onto DT, and was blown away further, and started actually giving a crap about the lyrics.
And then Opeth opened me to a whole new realm. The way they mix the growls with the singing, (while at the same time utilizing phenominal lyrics), and the acoustics with the distorted. Amazing.