Justin Timberlake at Jay-Z concert with girlfriend Jessica Biel

Justin Timberlake and girlfriend Jessica Biel get down to H to the Izzo at Jay-Z's concert at L.A.'s Pauley Pavilion.The 28-year-old singer and actor joined other celebs at the concert, including James Blunt, Jamie Foxx, Nicole Richie and Samantha Ronson .Rihanna also made a guest appearance at the show, singing "Run This Town" and debuting her new song, "Hard."Justin, who worked with Rihanna on her new album, told MTV last month that RiRi's new music is edgier than before. "The stuff we've come up with in the studio, it's the next step for her," he said. "It's a little more grown-up."