If you like heavy music, you'll love this game. Otherwise, it's still funny but you won't get some of its cracks.
You play a roadie that got himself to a Metal world in a bizarre way, and there he has to release its people from tyranny. This guy, Eddie, has an ax and a guitar, and along the way he learn a few tricks to help his cause. Most of the travelling in this world and most missions are with "Deuce", his ultra cool costume car. When traveling , you'll hear this game's awesome sounstrack, varying form early Sabbath to modern Black Metal. Most mission are battles - stage battles or plain hack and slash, and while fun at first, it gets repetitive. ( I finished the game doing after doing only 52% of the missions. After that, the game reveals all the secondary missions, most of them are more or less the same battles, or racing with the same crazy dude).
For each mission you get points that are used to improve your car, your weapons or the way you look.
You also discover at some special places new abilities that can be used during battles, done in a very short guitar hero style (didn't get it. Most of the time its 3-4 buttons pushed, and if you're doing it wrong, you still get the powers.)
The story is OK, but is told in a funny way, roadie/metal/music business lingo.
The main problem with this game is inconsistency - some parts are very hard (on Normal) and some are very easy. Same goes with production values - when you meet Metal Gods like Ozzy, Halford and Lemmy, its high and sharp, but control still feels ported, especially when you you drive around.
Regarding multiplayer - you can try and find someone online - good luck with that... this game went out for consoles in 2009, but got to PC just in 2013 (It seems this way).
Find it on 5$, you'll spend no more than 20 hours in a Metal world. You'll like the story, have some great battles, get a little frustrated, and in the end - it ends too soon...