Beyoncé Knowles donned a black leather leotard to rock the stage at yesterday's Chime For Change benefit concert, The Sound of Change Live, at Twickenham Stadium in London. She was also joined by her husband, Jay-Z, during her live performance at the show, which included her new song, "Grown Woman." Before taking the stage, Beyoncé posed backstage for pictures with Salma Hayek, who cofounded the charity, as well as Gucci Creative Director Frida Giannini. She's headlining the concert, which promotes education, health, and justice for girls and women worldwide, and she was joined by many other famous faces to support the cause. Jennifer Lopez heated things up with her hit "Live It Up" and also linked up with Mary J. Blige for a special performance of The Beatles' song "Come Together." Blake Lively, who left her London hotel with husband Ryan Reynolds earlier today, Madonna, James Franco, and Jessica Chastain are a few of the other stars who have already taken their turn at the mic, while Florence Welch and John Legend have also taken the stage. Plenty of other A-listers have descended upon London for the charitable event — click through to see all the stars at The Sound of Change Live!