Oooh, Great Monster Kevin!
I assume that one of his moves is 'Charge a group of enemies with abandon'? and that he has the tags forceful, messy and piercing?
I think its a wonderful move but the wording to me seems a little directive, and possibly hard to trigger as a move...
The trigger ties in with the 10+ result without being explicit. The 10+ result assumes that the player wants to avoid the charge (no problem) and expose a weakness. So maybe:
When you try and avoid the mighty metal minotaur's thunderous charge, roll +Dex
Or even:
When you stand firm against the mighty Metal Minotaur's Murderous Charge attempting to reveal his weakness, roll +Wis
That way its triggered as a specific player action (rather than a GM Move), and is inherently divergent from either Defy Danger or Defend or even Discern Realities... it also does snowball rather nicely from the Minotaur's Move (attack) I suggested above :)
Now the 10+ gives the player their intent and opens the fiction for another move too (based on the minotaur's vulnerability - nice!)
With the 7-9 result I would just give the options, and write in the Minotaur's 'exposure' as one of the choices. Thus:
On a 7-9, choose one:
*You are trampled underneath, take 1d10 damage, but you expose a weakness, what is it?
*You get in real near to a position of advantage, but the minotaur gores you with his rune-etched horns, doing 1d6 damage and healing himself the same amount.
*You are knocked back and into the air, landing in a place of safety. You are momentarily stunned with the wind knocked out of you.