Giant Mech-soldier + Meteor Dragon → Metal Dragon

Metal Dragon + Thunder Dragon → Twin-headed Thunder Dragon

Metal Dragon + Beautiful Beast Trainer → Vermillion Sparrow

Metal Dragon + 30,000-Year White Turtle → Sea King Dragon

Metal Dragon + Destroyer Golem → Stone D.

Metal Dragon + Barrel Rock → Stone D.

Metal Dragon + Minomushi Warrior → Stone D.

Metal Dragon + Stone Ghost → Stone D.

Metal Dragon + Kaminari Attack → Twin-headed Thunder Dragon

Metal Dragon + Tripwire Beast → Twin-headed Thunder Dragon

Metal Dragon + Bolt Escargot → Twin-headed Thunder Dragon

Metal Dragon + Bolt Penguin → Twin-headed Thunder Dragon