Fusion Summon is a special summoning method in the Yu-Gi-Oh! trading card game. It allows players to combine specific monster cards from their hand or field to create a more powerful monster known as a Fusion Monster. This process typically requires a Fusion Spell Card, such as Polymerization, which specifies the monsters needed for the fusion. To perform a Fusion Summon, players must have the required materials and the appropriate Fusion Monster card in their extra deck. Once the conditions are met, the selected monsters are sent to the graveyard, and the new Fusion Monster is summoned to the field, ready to battle.