To adapt a lyric from their biggest song to date, this band is on fire. And, judging by their output to date, literally reinventing their sound at a pace nearly reminiscent of the Beatles. For just as Sgt. Pepper sounded nothing like the Beatles who played Ed Sullivan a mere three years earlier, the Kings of Leon on last year’s epic Only by the Night seem light years removed from the scrappy Southern rockers responsible for 2003’s Youth & Young Manhood. In truth, they’re still the same Followill boys from Nashville — brothers Caleb, Nathan and Jared and first cousin Matthew — who took the U.K. by storm earlier this decade and later won over their homeland festival by festival with a sound suggesting a cross between Tom Petty’s Heartbreakers and the Strokes. By 2007’s Because of the Times, though, it was patently clear that this was not a band intent to spend its career cooped up in one style; all that touring opening up for the likes of U2, Bob Dylan and Pearl Jam expanded their musical horizons. Some fans might have jumped ship after the Kings shaved off their wooly mustaches and shifted seemingly overnight from fuzzy garage rock to the sophisticated but arena-swelling art rock of Because of the Times and Only by the Night, but the hits kept on coming. “Sex on Fire,” in fact, recently became the best-selling digital single of all time in the U.K. And the Kings of Leon are now well on their way to rock royalty on their own side of the pond, too.