That version of Metallo was the one who had his powers augmented by Neron.
Aftert that he had the power to absorb metallic objects he touched, adding them to his form. If Iron Man punches Mentallo, Metallo can absorb the armour.
He could simply touch the Iron Man armour and absorb it, upgrading his form with it's powers.
Iron Man could block this by using his forcefield but he does not have this field errected all the time (as it drains a lot of power and I don't think he can employ all of his weapon options when it is up).
Metallo is very durable and if he is damaged he can simply absorb other metallic items to repair himself, grow his mass and make himself stronger and more durable.
This version of Metallo is stronger than this version of Iron Man and Tony is sure as hell not gonna hack a hell powered cyborg.
"This is a good one. I'd give it to Iron Man. I just can't see Metallo coming out on top (though it'd be a decent fight). Strength-wise, Metallo's at best equal, but Stark's a genius. He could probably hack Metallo. "
@kneel before doom said:
"Tony can win while having an orgy with she-hulk and Ms.marvel 20 blocks away in the comfort of his own home. "