Recorded in July 2020, Willow Song was released on December 11, 2020, by Republic Records. The track is the lead single from the album Evermore.
It is a romantic chamber folk song that expresses the singer's romantic state of mind by using several metaphors. The track portrays her life as a willow tree and features instrumentation such as guitars, glockenspiel, strings, flute, and percussion.
The single was produced by Taylor along with Aaron Dessner and gained widespread critical acclaim upon its release. It appeared at number one on the Billboard 200 chart.
Willow also peaked at the number one position in several countries, such as Australia, Singapore, and Canada, and in the top 10 in countries including Belgium, Hungary, Croatia, Ireland, and Malaysia.