The Big 4 LIVE: Metallica, Slayer, Megadeth, and Anthrax [PHOTOS & VIDEO]

The "Big Four" bands of 1980s thrash metal - Metallica, Slayer, Megadeth, and Anthrax - performed for the first time ever on the same stage in the United States on Saturday, April 23rd at the Empire Polo Club in Indio, California in front of a capacity crowd of more than 50,000 metalheads.

Slayer guitarist Jeff Hanneman, who was forced miss all of the band's shows this year after undergoing emergency surgery on his right arm in January, made a surprise appearance during the group's set, joining his bandmates on stage for the two-song encore of "South Of Heaven" and "Angel Of Death". Exodus guitarist Gary Holt filled in for Hanneman during Slayer's main set.

The highly anticipated onstage performance of all four bands at the same time happened near the end of Metallica's set, between "Enter Sandman" and "Hit The Lights". Members of Anthrax, Slayer, and Megadeth joined Metallica on stage for a cover of Diamond Head's "Am I Evil?" before Metallica ended the night with its perennial set-closer, "Seek And Destroy" from the band's 1983 debut, "Kill 'Em All".

In introducing the members of the other three bands immediately prior to the "Am I Evil?" performance, Metallica frontman James Hetfield said:

Can you believe it? Thirty years, man. I don't know how many of you have been around that long, you know?! It doesn't matter; you're here right now to see the 'Big Four,' and we're getting this prepared for a big jam, alright? It's pretty important. We just wanna take the time to say 'thank you' to all of you metal fans out there who have supported all the bands — not only the 'Big Four,' but the big however many out there. There's many, many other bands that have been around as long as us, and, unfortunately, broke up because of business or some other crap. There's a lot of great bands out there and we'd like to celebrate all of them, and especially the 'Big Four', getting out here and jamming, and just saying 'thank you' to the world of metal fans for just giving us your support, giving us your heart and giving us your passion, man, 'cause that's what it is for us.