Its not necessarily the lyrical content that I like. If its beyond what I define as brutal, than I will listen to it, regardless of the lyrical content.
But if its all just "do this way, its the greatest, blah blah blah" subliminal messaging, then I won't listen to it.
Also, there has to be a certain level of brutality within the bands skill as musicians. If they can suddenly play insanely slow or ungodly fast, wow. Drums and guitar are a must in that field. Slow growls and/or squealing works too.