The 35-year-old Transformers actress was caught spewing out the f-bomb while arguing with her boyfriend of one year.
The exchange looked intense between the two, who hours prior couldn't keep their hands off of each other in front of cameras.
Photos and video backstage show Megan appearing agitated with her rapper beau.
At one point during the ceremony, the actress was caught mouthing "what the f*---" to 31-year-old MGK.
Megan then talked to someone else before walking out of camera range with her boyfriend.
Prior to their argument, the couple caused a stir with their PDA-filled red carpet appearance.
Megan flaunted her killer body in a barely-there black dress.
Rocking the curve-hugging number that had a plunging neckline and several cutouts exposing her bare skin, the Transformers actress wore black underwear to hide her bits in the mesh, see-through dress.
MGK wore a tux but kept it casual with an untucked and unbuttoned white shirt. He surprised everyone when while making a fashion statement with a painted black tongue.
It wasn't just the duo's shocking wardrobe choices that made eyes pop.
Megan made everyone blush when she took her hand and grabbed the rapper's junk in front of photographers on the red carpet.
MGK reciprocated and had his hands glued to his girlfriend's body.
The couple also shared a passionate kiss on television when Machine Gun Kelly accepted his Top Rock Artist award.
Megan and MGK are all about the shock factor and often take their PDA to the next level.
Their relationship is getting pretty serious.
According to PEOPLE, he’s even been spending time with her three children -- Journey, 4, Bodhi, 7, Noah, 8 -- who she shares with her estranged husband Brian Austin Green.
Their romance didn't start without drama though.
Megan Fox and Machine Gun Kelly were first seen holding hands in May, which caused a ton of controversy because no one knew she had split from her husband at the time. Days later, the Beverly Hills, 90210 alum came clean about their breakup.
In November, Brian Austin Green filed for divorce from Megan Fox after more than 9 years of marriage, leaving the door open for MGK to move right in.