The robot lions are five lions that combine to form Voltron. They come in five colors - black, red, blue, yellow, and green. The Black Lion forms the main body of Voltron, while the arms are formed by the Red and Green Lions, and the legs are formed by the Blue and Yellow Lions. The lions were formed when Hagar cast a powerful spell breaking up Voltron into five parts.
Each lion has a special key that is needed to unlock the lion's full potential.
The lions appear to have limited sentience, perhaps that of a biological lion, as shown by Black Lion slowing the descent of the Doom transport ship in which Keith and company escaped. It is clear that the lions can not assemble into Voltron without pilots.
Each of the lions has a head and four legs. The primary power source for the lions is an elemental power crystal, located in the lion's main body. The lions are individually capable of flight, hovering, and running. In addition, the head can detach from the body and is capable of independent flight. The cockpit for the lions is located inside the head, directly behind the eyes.
There are at least three entrances to the cockpit. One entrance is at the bottom of the neck, where the pilot's seat is lifted up from the lion's lair to the cockpit. The second entrance is a hatch on top of the lion's head. A third entrance is on the right side of the lion's head.
Each lion corresponds to a different elemental power.
The Black Lion corresponds with Lightning.
The Red Lion corresponds with Fire.
The Green Lion corresponds with Air.
The Blue Lion corresponds with Water.
The Yellow Lion corresponds with Earth.