Like the Yardrats, the Metamorans are responsible for teaching Goku a very useful and powerful technique. They are the inventors of Fusion that Goku teaches to Goten and Trunks. All that is known about the Metamorans is that Goku met them in the Other World. they taught Goku the technique at some point during that time frame. Any Fusion that is the product of the Metamoran Fusion Dance (including failed fusions) will wear Metamoran clothing. The Fusion only lasts 30 minutes.