He's Fast, She's Metal

Riley Bourne has always been a special girl. When she was 13 she ran away from home when she accidentally turned her arms in metal, she came back when they returned to normal only a short 30 minutes after the incident; when she was 16 she turned her whole body into metal, that lasted about 30 minutes also but that was long enough for her parents to become terrified of her. She ran away again, this time it was permanent; luckily she knows the famous Pepper Potts, this woman was her mother's old best friend and was always a second mother to Riley. This is how Riley became the unofficial daughter of Pepper and later Tony Stark.

Pietro Maximoff was never really anything special, he had a twin sister and a loving family. When a bomb kills his whole family, sparing himself and his sister, they vowed revenge on Tony Stark. Becoming lab rats to Wolfgang von Strucker, they became powerful; they had the means to destroy Tony and they planned on doing just that.

The two meet on the battlefield, and no they don't fall in love; they absolutely hate each other. Riley doing anything she can to protect her ironclad father figure, Pietro doing anything to try and bring him down.

Will there ever be anything between the two besides animosity? Probably, most likely, yeah.