Bring Me the Horizon share co-writing credit with Halsey on the singer's upcoming Birds of Prey soundtrack contribution, "Experiment on Me." It's a song the pop star called her "craziest song" ever in a recent Twitter exchange that confirmed the collaboration.

Yet it's not the first time that Halsey has partnered with the English rockers led by frontman Oli Sykes. It initially emerged last summer that Sykes and Bring Me the Horizon keyboardist Jordan Fish were working with the hit-making "Without Me" songstress in the recording studio. Then, last month, the metalcore-turned-pop band surprise-released their Music to Listen to… EP that included a cut featuring Halsey.

On Monday (Jan. 13), Halsey responded to some fan inquiries about the Birds of Prey tune. When asked if the song was one she previously previewed on Instagram, the singer likened the soundtrack number to the film's main character. That being the Joker accomplice Harley Quinn, portrayed by actress Margot Robbie.

"Experiment on Me!" Halsey replied. "For the birds of prey soundtrack. Hands down craziest song I've ever recorded. By a landslide. And rightfully so for Harley!"

After adding that the tune is "especially for Birds of Prey," the singer engaged yet another inquirer who thought they had mistaken the selection for a Bring Me the Horizon collaboration. "I wrote it with them!" Halsey explained.

The Birds of Prey soundtrack is due out Feb. 7 via Atlantic Records, as Billboard reported. It also features tracks by Doja Cat, Megan Thee Stallion, Charlotte Lawrence, Cyn and Jucee Froot. The movie itself, the latest entry in the DC Extended Universe, hits U.S. theaters the same day.