The fact that countrified rockers the Kings of Leon have the perfect back story has undoubtedly helped them achieve status as the latest alt-rock buzz band. The three Followill brothers, singer and rhythm guitarist Caleb, drummer Nathan, and bassist Jared, spent their childhood traveling the country with their father, a United Pentecostal evangelist. Their cousin Matthew Followill plays lead guitar. But whether or not the fire and brimstone of their youth fuels their zealous rock, their debut album, “Youth &Young Manhood,” has the passion of early Southern rockers like Jerry Lee Lewis, who were also raised in the shadow of hellfire. Album opener “Red Morning Light” has the swamp boogie grit of Creedence Clearwater Revival, while “Happy Alone” opens with a mounting melodic tension and slurred vocals reminiscent of the Strokes, before breaking into a country-rock rave-up. “Wasted Time” has a loose, stuttery rap fleshed out by sharp guitar fills and saucy lyrics like “I know all about the little games you play, shaking your apple right in my face.” While the opening intensity doesn’t last throughout the entire album, the manic breakdown that ends “Spiral Staircase” signals the return of the album’s gleeful intensity. “Holy Roller Novocaine” is a sultry mid-tempo rocker, carried by a low, cantering bass line and menacing vocals. Wherever they came from, and however they got here, the Kings of Leon play rock ‘n’ roll like their salvation depends on it.