Taylor Swift becomes Nelly's backing singer for surprise performance

Taylor Swift and sibling girl band Haim became backing singers and dancers for rapper Nelly during their concert in St. Louis, Missouri on Tuesday night (29Sep15).

The Shake It Off singer continued her run of shock tour appearances by inviting the hip-hop star onstage for a duet of his recent single The Fix.

Taylor's good friends and support act Haim then also appeared on the stage, and the trio, all dressed in white, performed a dance routine.

The showed off their best moves in the background as Nelly rapped his 2002 hit Hot in Herre, and they also provided backing vocals for the chorus and the spoken female lyrics.

"I loved getting to sing The Fix & Hot in Herre with @Nelly_Mo! What a way to end @HAIMtheband's run on the 1989 Tour", Taylor later wrote on Twitter.com after posting video footage of the show.

Taylor has thrilled fans on her 1989 world tour by bringing an array of stars onstage to duet with her, including Justin Timberlake, Avril Lavigne, and Alanis Morissette.