Lucario & Melmetal-GX (UNB #224)

For the rest of this game, your Metal Pokémon take 30 less damage from your opponent's attacks (after applying Weakness and Resistance). If this Pokémon has at least 1 extra Energy attached to it (in addition to this attack's cost), discard all Energy from your opponent's Active Pokémon. (You can't use more than 1 GX attack in a game.)

Search your deck for a Metal Energy card and attach it to this Pokémon. Then, shuffle your deck.