Watch Taylor Swift, Nelly and Haim Perform 'Hot in Herre' in St. Louis

With Taylor Swift out on tour, expect two things: All-star guests making surprise appearances – just this weekend, she welcomed Steven Tyler and Mick Jagger to the stage – and Nelly coming out for her St. Louis shows. Swift’s 1989 Tour descended on St. Louis Tuesday night, and as is tradition, Nelly was on hand at…