The song's success is being lauded for the fact that it marks the first time that an openly transgender and a non-binary solo artist, respectively, have landed on the No 1 spot of the Billboard Hot 100 charts.
Purveyor of unapologetic pop
"I am so grateful," Petras wrote in an Instagram post. "Sam, I can't thank you enough for being with me for years. I'm so honored to be a part of your first number one in the US … I love you forever angel Sam."
Petras, who was born in the German city of Cologne in 1992, moved to Los Angeles at age 19. In a 2018 interview with DW, she described how she initially slept on couches in studios, had little money and very few contacts. "Every day, I wrote three or four songs, I got to know people, and I contacted them on the internet."
When asked back then for her reaction to Lady Gaga's ex-manager, Troy Carter, describing her "as the best thing in the world of pop since Gaga's debut," Petras had said that she sings what she called "unapologetic pop."
"That had been missing before. I write my own lyrics, I can incorporate my own ideas. And yes, apparently, people think it's cool. That's pretty awesome," she told DW.
She has since made a name for herself in the US and has toured with the likes of Camila Cabello, Charli XCX and Rita Ora.
'Unholy' is the biggest US hit of Petras' career so far, while it's Smith's highest-peaking hit on the chart since 'Stay With Me' reached No. 2 in 2014. 'Unholy' had already started becoming viral when Smith shared a snippet of the song on TikTok in August.
'Best feeling in the world'
In 2018, Petras told DW that she doesn't specifically write songs about transsexuality.
"Maybe some day I will. But I actually prefer to write about topics that are relatively normal. I find my emotions are inspiring, but I don't find transsexuality to be that inspiring."
Speaking to Billboard last week when her song was still at No 2 she said: "I just really don't want to be the last."
"There's always been incredible and talented trans artists. I'm just happy that Sam gave me the chance to shine here. It feels like people are finally ready for us to succeed, and that fills me with a lot of joy."
Meanwhile Smith, who identified as non-binary in 2019, recently told Billboard, "People understanding us… is just the best feeling in the world. Because there's nothing bad happening here, it's all love. No one's taking anything from anyone. People are just trying to live in their own skin on this earth."