The first type of fusion that we see in the series is the Namekian Fusion . This type of fusion is exclusively for Namek's. First, one Namek places his hand on the other, then ki is concentrated and the fusion begins to take place. The Namek's have the ability to choose which of the two bodies they want to use. The resulting warrior is very powerful, depending on the strength of the two warriors. If by chance the two warriors fusing were once one being and parted for whatever reasons, the Fusion becomes twice as powerful.

The second fusion shown in the series is the Fusion Dance .
First, the two warriors must be equally strong and close in size. Then in order for the fusion to work properly, the two must perform a dance. Any mistake in the dance will end up in a deformed fusion. While performing the dance, the two must yell Fu..sion..ha. If done properly, the 2 will become much stronger than ever before. However, it only lasts 30 minutes, and if the warriors are Saiyan and in the Third Super Saiyan level, they can only stay fused for 5 minutes. The fused warrior has a combined attitude from both people, but is a completely different person.

The third and last fusion is the Potara Fusion . The Potara are earings that each of the high ranking Kais wear. When taken off and put on the opposite ears of two people, the Potara pull the people together, creating a new entity. Elder Kai gives his Potara to Goku during the Buu Saga, and Goku fuses with Vegeta, creating the warrior Vegito. The attitude of the new warrior is a combination of the two, but it tends to lean towards one more than the other. No requirements--other than the Potara be on opposite ears--are required. This fusion is just a tad bit weaker than the Fusion Dance, but it is still a very good powerup and will last forever.

Absorption isn't really a kind of fusion but it does take multiple beings and make them become one so thats good enough for me. Cell and Buu are the main people to absorb beings and they did so big either eating the other being or in Cell's case sucked them through his tail. The increases that he gains rivals that of Super Saiyans. If Cell is hit hard enough though, he will regurgitate a product of the absorption, such as an android, and become less powerful.