If Clefairy or Clefable used Metronome Wildfire
against a Moltres, then would the opponent discard
their deck? Metronome copies the attack except for
discards and energy costs and Wildfire can make the
opponent discard as many cards as you want. Thanks.


This is a rather good question.  I will explain why this is not broken:

Clefable does not have to pay additional costs, such as discarding energy to Charizard's Fire Spin, to make it work.  Moltres is a whole different demon, though.  It's Wildfire attack only costs 1 fire energy, and by itself has no effect.  It does have an additional attack clause, that says if you wish, you may discard any number of Fire Energy.  If you choose to do so, then your opponent discards that many cards from the top of their deck.  This is not a required cost, as it does not HAVE to be paid - you CAN Wildfire for 0.  That is why it does not work that way.

Scott