Post Malone featured in Taylor Swift's "The Tortured Poets Department"

The intrigue: "Fortnight" is the album's opening song and lead single.

What she's saying: "I've been such a huge fan of Post because of the writer he is, his musical experimentation and those melodies he creates that just stick in your head forever," she wrote in an Instagram post ahead of her album's release.

• "I got to witness that magic come to life firsthand when we worked together," she said.

Driving the news: Swift released her 11th studio album on Friday.

• Florence & the Machine is also featured.

Between the lines: Post Malone was also included in Beyoncé's "Cowboy Carter" track "Levii's Jeans" released on March 29.

What's next: A music video of "Fortnight" is expected to drop Friday at 6pm (MT).