Taylor Swift will sing a duet with a teenage contestant on the season finale of America's Got Talent on Tuesday night (Aug. 21) on NBC. Swift will perform with 14-year-old Juliette Irwin. Pop singer Sean Kingston ("Beautiful Girls") will also appear. The winner among the four amateur finalists will receive a $1 million prize. Swift says she's looking forward to working with Irwin. "She's such a sweetheart, and I'm so unbelievably honored that she chose me as her duet choice," she said. "She's got such a powerful voice, and her story is so endearing. I want her to win!"