This is one of those things that's so weird/random that we wouldn't have believed it if, say, one of our friends was like, "Yo, did you hear that mashup El-P did of Metallica and Prince?! It's AWESOME!" This would have induced much eye-rolling and "Yeah, OK"s until we, of course, actually found it online and heard it for ourselves.
So, yeah, El-P apparently felt the need to create the mashup after talking about which two artists are most against downloading and piracy. As you'll probably agree, I don't think there's anyone more deserving than Prince and Metallica. Hearing perhaps their biggest hits -- "Purple Rain" and "The Unforgiven II," respectively -- mashed together is terribly appropriate. And awesome.
You can stream the mashup below and download it at Consequence of Sound.