The biggest stars in pop arrived at the Billboard Music Awards in Las Vegas, where organisers have defended their decision to choose Madonna to pay tribute to Prince.
Purple Rain star Prince, 57, who died suddenly last month, will be honoured at the ceremony, which marks one of the biggest nights on the US music calendar.
Adele leads the British charge with eight nominations, while David Bowie is up for a posthumous award for his album Blackstar.
Britney Spears was among the first stars to arrive on the pink carpet at the T-Mobile Arena, where she will receive the Billboard Millennium Award for her "career achievements and influence on the music industry".
The Baby One More Time singer opened the show with a medley of her biggest hits and is only the third artist to receive her award after Beyonce in 2011 and Whitney Houston in 2012.
Kesha performed at the awards after her ex-producer's record label overturned its refusal to approve her performance.
It followed concerns she would refer to her legal dispute with producer Dr Luke, who she accused of drugging, sexually abusing and emotionally tormenting her. He vehemently denies the allegations.
Madonna wiil pay tribute to Prince despite an online petition calling for other musicians to be involved in the homage attracted thousands of signatures.
The petition, which has been signed by more than 8,000 people on Change.org, claimed Prince was "more than worthy of a better choice as a main performer".
But Mark Bracco, executive producer of the awards show, said Madonna's tribute would be "very intimate and very respectful". It was later announced that The Roots musician Questlove would join her for the performance.
Celine Dion was presented with the Icon Award, Billboard's lifetime achievement honour, after a traumatic start to 2016 for the singer.
Her husband Rene Angelil and brother Daniel both died from cancer just days apart in January. Dion, 48, performed Queen's The Show Must Go On at the ceremony.
The star-studded line-up of artists performing also includes Rihanna, Justin Bieber, Pink, Ariana Grande, Meghan Trainor, Gwen Stefani and Blake Shelton.