Iron Body is one of Zangief's Hyper Combos.
Zangief enters a state of hyper armor and is called Mech-Zangief. He turns metallic grey and continues to fight. In this form he will not flinch from most attacks, but he is not allowed to block. Zangief will stay in this form until he gets K.O'ed or by inputting the same command that activated Iron Body, he will revert back to his form.