After Green Day was forced to cancel their New Orleans Voodoo Experience headlining date to allow for Billie Joe Armstrong to continue rehabilitation, it left a huge hole in the festival schedule.

Fortunately for event producers, they were able to trade one giant band for another. Metallica not only stepped up to the plate but after just two songs, frontman James Hetfield paused to pay tribute to Billie Joe Armstrong and his band. According to MSN, Hetfield joked, “We… Are… Green Day! Except a little taller!” The singer later dedicated the song “Battery” to Armstrong, saying, “This one’s for Billie.”

During Metallica’s encore, Hetfield remarked, “You’re hoping Green Day is going to show up, right?” To which the audience of thousands booed. “He’s there gettin’ help, all right? Getting it sorted out. We’re here stepping up for ‘em, hoping he gets it together, cause the world needs him, all right? I think so.” Without pause, drummer Lars Ulrich started the well known opening drum line to Green Day’s “American Idiot.” Hetfield followed with Armstrong’s signature guitar riff, and swiveled the mic toward the crowd to fill in the vocals.”

As Billie Joe Armstrong remains in rehab, Green Day has moved to cancel all remaining concert dates and public appearances for 2012 and early 2013. Moreover, the band moved up the release date for ¡Tre!. Originally scheduled for a January release, the third installment of the trilogy will now go on sale December 11, 2012.

In a statement posted to the band’s website yesterday Tré Cool said “We feel bad we have to delay our tour, so to make up for it we want to give our fans the music earlier than we had planned. If we couldn’t be there to play it for you live, the least we could do was give you the next best thing.”

– Jay Tilles, CBS Local