Last month, Green Day were forced to cancel a number of shows after frontman Billie Joe Armstrong went into rehab for suspected alcohol abuse. One of the affected dates was their headlining slot at this past weekend's Voodoo Festival down in New Orleans, but luckily Metallica were able to jump in at the last minute. Guitarist Kirk Hammett stated that they took the opportunity in deference to Green Day. "We discussed it between the four of us and we all said, 'Yeah.' It would be great thing for us to do and it would also be great to help out Billie Joe, 'cause he's a friend of ours and we love Green Day. If we can help them out in any way possible, we're always happy to do it, 'cause we love those guys. It's actually an honor for us that they approached us and asked if we can fill in."
And as a token of their respect towards the pop-punkers, Metallica threw in a cover of Green Day's "American Idiot" into their headlining set. Well, sort of. Frontman James Hetfield and drummer Lars Ulrich launch into the song, but it's pretty apparent they don't know the whole thing. Hetfield doesn't even sing--he turns the mic onto a surprised crowd, which half-heartedly shouts the words before the song self-destructs. "That's all we had time to learn," Hetfield quips. Watch the semi-performance (along with Metallica's "Creeping Death") below. [Spin]