Metallica have stepped in to replace fellow north Californians Green Day as headliners at the Voodoo Music + Arts Experience festival in New Orleans, Louisiana over Halloween weekend (26-28Oct12).

The heavy rockers have taken the punk trio's Saturday night slot on the bill after the 21 Guns hitmakers were forced to pull the plug on their appearance due to singer Billie Joe Armstrong's substance abuse issues, which landed him in rehab last month (Sep12).

The set will be Metallica's first at the New Orleans festival.

Drummer Lars Ulrich says, "We are excited to be part of our first ever Voodoo Music + Arts Experience. Our good friends and fellow Bay Area residents Green Day had to unfortunately cancel their plans to be there, so we are more than happy to fill in for them in our own unique way. We’re hoping we can fill those very large shoes and do them proud."

Green Day drummer Tre Cool announced his band would not be playing at the festival earlier this week (08Oct12), stating, "We had to put the life of our friend in front of everything."

Armstrong is still recovering from a health crisis which led to a meltdown at a show in Las Vegas.

The rocker checked himself into a treatment facility the following day for substance abuse issues.

On Friday (12Oct12), Warner Bros. Records chairman Rob Cavallo, Green Day's longtime producer, released an update statement about the punk icon, and revealed, "His rehab is no joke. He's under medical supervision for a while to get him clean."

Cavallo fears more shows will be cancelled to accommodate the star's recovery: "His doctors are still evaluating. All I can say is I don't know if we'll see him before or after Christmas. It's basically undetermined when he'll be back."