Yugioh question Can metalmorph be activated in response to an attack by your opponet and be equip to the attacked monster

Because Metalmorph changes the ATK of a monster, it can be activated in the Damage Step. You can therefore do two things.

If the defending monster is face-up already, you can activate Metalmorph in response to the attack, that's fine.

If the defending monster is face-down, you will flip it at the start of the Damage Step, and can activate Metalmorph as above, before you enter Damage Calculation.