"Happy Z Day," Swift, 27, captioned the brooding photo of herself and Malik.
The song is the first track released by Swift since her 1989 album dropped in October 2014 -- and it's climbing the charts. Currently, "I Don't Want to Live Forever" is number 11 on Billboard's pop chart, with Malik's former One Direction bandmate Niall Horan's track, "This Town," coming in at number 12.
"I Don't Want to Live Forever" was written by Swift, Sam Dew and Fun's Jack Antonoff, who also worked with Swift on her song, "Out of the Woods."
Fifty Shades fans were able to preorder the movie's soundtrack on Friday, which will allow them to download Swift and Malik's song, as well as Halsey's track, "Not Afraid Anymore." Other artists on the album include Nick Jonas, Nicki Minaj, Sia, John Legend, Halsey, Tove Lo, Kygo, The-Dream and Corinne Bailey Rae.
The sequel's soundtrack will be released on Feb. 10, the same day that the movie arrives in theaters.