5 Seconds of Summer began on YouTube and was the opening band for One Direction in a 2013 tour, but now the music has taken on a life of its own (including a 7.4M Twitter following). The band consists of Luke Hemmings, Michael Clifford, Calum Hood , and Ashton Irwin, all of whom are 21 years-old or younger. The band bases its music on a whining, punk, almost-90's feel that helps them promote a "we're young and we don't care" message that fans seem to love. According to Daily Mail, "She's Kinda Hot" was the most shared song on Twitter on Tuesday.