I'd qualify myself as a metal fan. I've been listening since the end of the 80s and have been to dozens of concerts. I like Dethklok's music, but Metalocalypse confounds me at times. It doesn't hold my attention the way I wish it would. Apparently Metalocalypse was popular enough that they expanded the show to a full half hour (22 min. actual time). I consider this show to be somewhat of a satire on the music business in general, not a satire on metal. In that respect, it's just a fanboy's fantasy.
One thing I just can't seem to grasp is the point of the conglomerate that tracks Dethklok. They mostly provide some exposition on the episode's plot which really doesn't need it, this is not a complex show. Other than that they seem to have some master plan, but I can't gather if it's for good or evil or what.
And in this season, for a show about the world's most popular "death metal" band ever, they often include musical numbers which are not metal at all. Maybe this is the result of the increased episode time, but these are a couple of the things that keep me from really getting into this show. Band member personalities flip-flop to extremes. It's just a little too scattered and not based enough in reality. I suppose that's why it was on Adult Swim. Maybe it wasn't meant to be a continuous storyline but became one.