"'Source: Yugioh Wikia'"
Fusion Monsters, colored violet, are cards representing a combination of two or more monsters. Fusion Monsters may only be included in the Fusion 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 Fusion Deck. However, they may be sent to the Graveyard when destroyed, as well as Removed from Play.
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. 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 some 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.
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. Most Fusion Monsters need two Fusion Material monsters, and then the Polymerization card. However, certain monsters such as XY-Dragon Cannon only need the monsters on the field, and can combine without Polymerization.
Types of Monster Cards
Types of Spell Cards
Types of Trap Cards
Other Types of Card
ATK - DEF - Level - Rank - Attribute - Type
Playing Field Zones
Types of Summon
Types of Monster Effects
Types of Effect Monsters
Types of Spell Speed
Aqua - Beast - Beast-Warrior - Dinosaur - Dragon