Before the stars took their seats at the Billboard Music Awards in Las Vegas Sunday, they had to strut their stuff on red carpet.

Upon arriving at the MGM Grand Garden Arena, Carrie Underwood, dressed in a strapless Oscar de la Renta ball gown, posed with her husband of nearly two years, Mike Fisher. The hockey playing hottie, whose face was clean-shaven and without his playoff beard, nestled himself behind his wife's giant tulle skirt in one of the couple's rare red carpet appearances together.

Another head-turning moment of the night involved who else -- Justin Bieber, whose arrival caused a mob scene with fans, reporters and photographers flocking to the 18-year-old pop star. Bieber later took the stage (and the award for Top Social Artist) to perform his first single off his new album Believe, "Boyfriend."

Watch the video clip above to see Katy Perry, Taylor Swift, Natasha Bedingfield, Jordin Sparks, The Wanted, Nelly Furtado, Brandy, Alicia Keys, LMFAO and other stars take the red carpet.