FOXBOROUGH -- Is it possible to sell millions of records, win Grammy Awards, employ saxophones in your rock opera, and still be punk? Green Day leader Billie Joe Armstrong has wrestled with this dilemma for more than a decade -- on 1995's ''Insomniac," he skewered mall culture and his band's platinum-selling soundtrack to it -- and he's jousted as often with himself on this subject as with both the Berkeley trio's detractors and supporters.
But if punk has anything to do with a principled political stance leavened by self-mockery and a healthy sense of the absurd fed through loud, fast guitars, then Green Day is it. And, quite frankly, a universal triumph such as last year's ambitious ''American Idiot" makes the question moot. Instead, what Green Day has quite possibly become, to repeat the plaudit accorded the band by openers Jimmy Eat World, is ''the biggest band in the world."