Energy is the nuclear power source of all robots in Metal Arms: Glitch In The System, and the source of players' health points. Appearing as a glowing green Bohr-model nucleus atom, it can be found all over Iron Star, and when Glitch takes damage, he loses Energy, and must find more to stay alive.
On Iron Star, according to the Droids, Energy is made underground by the mysterious Morbots, and is what powers robots to move around and think, as well as providing a force field which holds the Droids' and Milbots' metal bodies together. Once a robot has no Energy left to keep it stable, a single hit from anything can destroy it. Droids and Mils keep their Energy in containers in their chassis called Batteries; most robots on Iron Star have one Battery, but Glitch can find up to 5 more throughout the game, and each one he finds will be full of Energy.
It can be found in many locations. Killed enemies will occasionally drop Energy, it can be purchased from Shady and Mr. Pockets cheaply with Washers, starting a new mission refills your Energy, and it can be found simply lying on the ground.
Energy from Glitch's Batteries is also the power source of the Mining Laser, although firing it uses so little Energy that the Mining Laser essentially has infinite ammo.