For example, the Elemental Hero Fusion Monsters have a clause stipulating that they may not be Special Summoned unless they are being Fusion Summoned. There are some Fusion Monsters that have special Summoning Conditions. In order for a Fusion Monster to be returned from the Graveyard to the field, it must be Fusion Summoned properly. If a Fusion Monster is Special Summoned to the field via a card such as Metamorphosis, and then sent to the Graveyard, it cannot be Special Summoned to the field from the Graveyard with cards such as Premature Burial, Call of the Haunted, or Monster Reborn. Monsters used with Polymerization are called Fusion Material Monsters. Originally, the only way to properly summon a Fusion Monster was through a Fusion Summon involving the required cards as well as Polymerization. In Yu-Gi-Oh 5D's Synchro Monsters appear to have filled this position. In Yu-Gi-Oh GX, however, introduced many fusion cards and many powerful fusion monsters were released during this time. In the anime, the original didn't use them a lot. However, they may be sent to the Graveyard when destroyed, as well as removed from play.

If a Fusion Monster is returned to its owner's hand or Deck, it is instead sent back to the Extra Deck. Fusion Monsters may only be included in the Extra Deck, and cannot exist in the hand or Main Deck.

Fusion Monsters, colored violet, are cards representing a combination of two or more monsters.

Metamorphosis yu gi oh