The cartoon in question is Metalocalpyse, another fine [adult swim] number that both ridicules and celebrates all things metal in equal parts.
In the cartoon, Dethklok are a metal band so popular that they have become the world's twelfth largest economic power.
But dig this; there's a real life Dethklok too, fronted by the creator of Metalocalypse, Mr Brendan Small. And they're not shit!
But it's the cartoon I've been watching. It might be a bit puerile and childish; but fuck it, so am I.