The 30-year-old musician took to Instagram on Sunday to share a carousel of images and footage of the pair together.
In his caption, he claimed that he wears Fox's blood around his neck. Sure enough, one of the pics featured a vial that appeared to contain a drop of blood and was hanging from a necklace. (See, we meant it literally when we called his post "heartfelt.")
"i wear your blood around my neck," he wrote, adding emojis that symbolize a knife, a drop of blood, a DNA symbol and a rose. "my bloody valentine."
On the same day, Fox also shared a carousel to her Instagram of video and photos featuring the couple in honor of Valentine's Day.
"there goes my heart," she wrote, "manifest outside of my body draped in the towering silhouette of a most unusually handsome boy magical and haunted kinetic and tortured ethereal and dangerous cosmic lawless eternal creative genius."
The 34-year-old "Teenage Mutant Ninja Turtles" actress continued, "the journey will likely be perilous but there is no destination without him happy valentine's day rehab barbie."
Included in her carousel was footage of Fox holding onto his waist from behind him while she had her feet on top of his as he walked her around the room. Machine Gun Kelly, whose real name is Colson Baker, shared this video to his Instagram Story.
Additionally, one of the pics Fox posted showed the "My Ex's Best Friend" rapper licking her pursed lips.
As fans recall, Angelina Jolie and Billy Bob Thornton famously wore vials of each other's blood around their necks during their short-lived marriage in the early 2000s.
It's appropriate that Machine Gun Kelly mentioned the words "my bloody valentine" in his post, as Fox appears in his music video for his single "My Bloody Valentine." The steamy spot debuted in May 2020, just as rumors had started to spread about the pair's then-budding romance.