Billie Joe in rehab; Green Day apologizes Tre Cool, Billie Joe Armstrong and Mike Dirnt (L-R) of Green Day arrive for the MTV Video Music Awards at Staples Center in Los Angeles on September 6, 2012. 24 (UPI) -- Green Day says its lead singer Billie Joe Armstrong has checked into rehab after his expletive-ridden, on-stage rant during a Las Vegas music festival. "Billie Joe is seeking treatment for substance abuse," the band said in a statement on its website Sunday. We would like everyone to know that our set was not cut short by Clear Channel and to apologize to those we offended at the iHeartRadio Festival in Las Vegas. We regretfully must postpone some of our upcoming promotional appearances. Armstrong halted the group's performance at the weekend festival after he spotted on a camera a 1-minute warning message to wrap up, then used the F-word more than a dozen times to loudly complain about the set being cut short to make way for other acts.