Bonnaroo fest opens with Metallica, Chris Rock

Metallica's Lars Ulrich and Kirk Hammett introduced Rock, and the comedian in turn introduced who he called "the baddest ... band in the world." Both acts were unlikely fare for the Bonnaroo Music & Arts Festival, which began in 2002 as primarily a jam band event.

But in recent years, Bonnaroo has broadened itself and brought more diverse fans to its 700-acre countryside site south of Nashville. Among the tens of thousands of festival-goers, Rock, Metallica and many other performers were very conscious of their entry into a tie-dyed world they seldom traffic in.

In a bit in his set about Prozac and other medications, Rock chastised the crowd, who he said was likely on "performance-enhancing drugs."

"You all should be ashamed of yourselves for taking antidepressants to see a comedian," joked Rock. "I am an antidepressant!"

Metallica also touted its cheerfulness.

"Do you feel good?" lead singer James Hetfield asked the crowd. "Metallica is here to make you feel better."

Performing on the main stage Friday night, Rock jumped right into his material, much of which he's performed during recent touring. Looking on backstage were many of the other comedians performing at the festival, as well as Jack White, whose band the Raconteurs took the main stage earlier in the day.

Rock worked the giant crowd without missing a beat in his timing, hitting on the election, Anna Nicole Smith and high gas prices despite the war in Iraq, ("If I invade IHOP, pancakes are going to be cheaper in my house," he said).

Metallica had a more difficult time winning over the crowd, which was head-banging but apparently not moshing. Hetfield repeatedly urged the audience to sing along. He asked, "We do have a few Metallica friends here, yes?"