Amon Amarth is some excellent Viking metal.

Alestorm is entertaining pirate metal.

Valient Thorr has a shtick where they claim to be sent from Venus (although musically, I grew to like them less the more I listened to them).

Okilly Dokilly was a Ned Flanders themed metal band (although again, I'm not particularly recommending them, as I really didn't care for the one song of theirs I heard).

Austrian Death Machine was a side project of the frontman of As I Lay Dying (the one who served time in prison and has since been released) based entirely on Arnold Schwarzenegger movie quotes

I'm sure there are a ton of others I'm not thinking of off the top of my head, but these are the first ones that jump to mind.