When we interviewed Tim Schafer a while back he talked about how hard it was to come up with the multiplayer portion of
Brutal Legend but that he was pretty happy with the result. Since then we've gotten some looks at what the multiplayer component is going to be and it doesn't look too bad.
In the game you can take one of three sides and then fight it out in a semi-RTS method as you try to take down your enemies stage (base). Here's the full explanation from EA