Sunday's iHeartRadio Music Awards teased a surprise during Madonna's performance, and a surprise she did deliver: Taylor Swift turned up to play acoustic guitar on Madonna's new single, "Ghosttown." With the duo starting side by side on stools, the number began as an intimate, light-some-candles-and-sway ballad and turned into an electrifying meeting of the souls -- specifically the souls of the biggest pop star of the moment and the biggest pop star of all time. Not just anyone can book Taylor Swift as a backup guitarist, after all.
Both singers posted joyful reactions on Instagram after the performance:
Madonna reappeared shortly thereafter to present Swift with Song of the Year, which she won for "Shake It Off":
RELATED ON HUFFPOST:
HuffPost Entertainment is your one-stop shop for celebrity news, hilarious late-night bits, industry and awards coverage and more — sent right to your inbox six days a week. Learn more