Fusion Monster

Fusion Monsters, colored violet, are cards representing a combination of two or more monsters. Fusion Monsters may only be included in the Extra Deck, and cannot exist in the hand or Main Deck. If a Fusion Monster is returned to its owner's hand or Deck, it is instead sent back to the Extra Deck. However, they may be sent to the Graveyard when destroyed, as well as removed from play. According to the anime, the Millennium Scale was the item which originally fused monsters. In the original Yu-Gi-Oh! they weren't used very often. In Yu-Gi-Oh GX, however, introduced many fusion cards and many powerful fusion monsters were released during this time. In Yu-Gi-Oh 5D's Synchro Monsters appear to have filled this position.

Originally, the only way to properly summon a Fusion Monster was through a Fusion Summon involving the required cards as well as Polymerization. Monsters used with Polymerization are called Fusion Material Monsters.

In a turbo duel Speed Fusion is the substitute for Polymerization.

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. In order for a Fusion Monster to be returned from the Graveyard to the field, it must be Fusion Summoned properly.

There are few Fusion Monsters that have special Summoning Conditions. For example, the Elemental Hero Fusion Monsters have a clause stipulating that they may not be Special Summoned unless they are being Fusion Summoned. This also rules them out from being Special Summoned either from the Graveyard or when removed from play. Others may disallow the use of Fusion Substitute Monsters, and in even rarer cases, both of these conditions may be applied, such as in Rainbow Neos.

With the Duel Terminal - Pulse of the Trishula, Fusion Monsters have started to come back with Naturia Extrio. Then in the booster packs Duelist Revolution and Starstrike Blast, 4 more Fusion Monsters was added: Ultimate Axon Kicker, Dragon Knight Draco-Equiste, Gaia Drake, Knight of Earth and Sky and Supreme Trainer Arcanite Magician. These 4 Fusions are the next evolution of Fusion Monsters. The first evolution was the standard Fusion requiring 2 regular or Ritual Monsters, for example Flame Swordsman. The second evolution of Fusions Monsters require at least 1 other Fusion Monster, for example Dragon Master Knight. The third, and current evolution requires at least 1 Synchro Monster, for example Gaia Drake, Knight of Earth and Sky.

Fusion Monsters even have their own Equip Spell Card: Fusion Weapon.

Polymerization support cards include Synchro Fusionist, Fusion Sage, Elemental Hero Woodsman, King of the Swamp.

Chain Material gives you access to any possible Material Monsters, except those removed from play.

Here are the cards you can use to properly Fusion Summon a Fusion Monster:

"Anime and manga only"

And a few ways to Special Summon a Fusion monster:
 * Re-Fusion to Special Summon a Fusion Monster from the Graveyard.
 * The VWXYZ Series and Armityle the Chaos Phantom "Union Fusion"
 * The Elemental Hero Neos and Gladiator Beast also Chimeratech Fortress Dragon Fusions "Contact Fusion"
 * The "Hex-Sealed Fusion" Monster Cards (The Earth - Hex-Sealed Fusion, The Dark - Hex-Sealed Fusion, The Light - Hex-Sealed Fusion)

1 Fusion Material Monster can be replaced by Fusion Substitute Monsters in Fusion Summons with cards that either do not specifically state the monster to be used as a Fusion Material Monster, or do not have a summon condition that limits either what monsters may be used for the Fusion Summon, or in what way it may be summoned.

A few Fusion Monsters can be summoned from the Extra Deck by a process known as Contact Fusion, which doesn't require a Polymerization card. So far, these are only used in "Neos" and "Gladiator Beast" fusing.