Heavy metal isn't really about nice tunes you can hum along to. Heavy metal is supposed to be challenging to listen to, it shouldn't be easy listening background music.
I've been a metal fan for a very long time and I have never listened to some Crowbar or Suicidal Tendencies and thought "if only this had a more catch tune and maybe a major key to cheer it up a bit". If I ever have those thoughts then I'll trade in my record collection for Michael Buble's greatest hits.