Justin Bieber goes shirtless at Rehab

Justin Bieber goes shirtless at Rehab
Justin Bieber hosts at the Rehab pool party at the Hard Rock Hotel. (Erik Kabik Photography/Retna Ltd.)

Pop star Justin Bieber took over Rehab, the dayclub at the Hard Rock Hotel, on Saturday afternoon before walking into the MGM Grand Garden Arena with boxer Floyd Mayweather Jr. that night.

Biebs showed off his Calvin Kleins and posed for photos with Australian model Shanina Shaik, actor Kyle Massey and friends.

Resident deejay Loczi dropped Bieber's song, "Wait For A Minute," as he ran back and forth across the stage with a friend to scope out the crowd. Bieber got on the mic to let everyone know that he was cheering for Floyd "Money" Mayweather before performing his latest single, "Where Are Ü Now."

Bieber danced on stage, took pictures with guests, shook hands with his fans and sprayed champagne showers over the partygoers.

Rappers Flo Rida and Red Café showed up at the pool party later to do an impromptu performance to "G.D.F.R" and "Low."