Metallica, Megadeth, Slayer and Anthrax heading to Yankee Stadium Sept. 14.
O'Brien will fill in for Exodus' Gary Holt, who has been subbing for Jeff Hanneman while he recovers from an injury.
The guitarist will replace Jeff Hanneman, while he recovers from surgery, on Slayer's upcoming Australian tour.
Metallica, Slayer, Megadeth and Anthrax will be sharing the same bill for the first time ever in America.
The SoCal thrashers will be releasing a previously unheard track, "Atrocity Vendor," as part of a special limited-edition 7-inch single.
This will mark the first U.S. tour Anthrax has done since vocalist Joey Belladonna rejoined the band earlier this year.
Slayer will see their ten American Recordings albums released as a limited-edition, high-end box set.
War at the Warfield, Still Reigning and, for the first time ever, 1995's Live Intrusion will be made available on DVD.
The California thrashers have just released the brutal new video for the title-track off their latest album, World Painted Blood.
Here's a glimpse from last night's Sonisphere Festival in Warsaw, Poland, which was the first time thrash's Big Four ever shared the same stage.