Rihanna matched the white carpet at today's Billboard Music Awards in a white shirt and pants combo. She's opening the awards show and tweeted, "Billboooooaaaaarrrrrrddddsssss!!!!!! In THE VEGAS!!! Don't forget to watch me open up the show tonight! #RihannaNavy I love you guys." Britney Spears will also be joining the star on stage to perform their remix of Rihanna's sexy hit "S&M." It will be a big night for the flame-haired singer as she's leading the nominations with a potential 18 awards to take home!