Proto Man was the original Bioroid designed and built by the scientist Thomas Light. Before his completion however, he was taken by Light's assistant, Albert Wily, to develop the ultimate destructive robot based on Proto Man's design. Being incomplete, Proto Man's energy core was unstable and nearly destroyed him. Wily attempted to repair him with his design for the robot type "Sniper Joe", but was only able to delay Proto Man's inevitable core failure. A part of these repairs shorted out, causing the development of an irregular matrix, which gave Proto Man the capabilities of free-will. After Mega Man's initial attacks on Wily, Proto Man was outfitted as a battle robot and given an impenetrable shield so that he may destroy his "brother". After a few brief conflicts with Mega Man, Proto Man rebelled against Wily and struck out on his own. Dr. Light offered to fix Proto Man's core, but he refused, knowing that if his core was fixed, he would lose his free-will. Proto Man instead chose to separate himself from the others and act only as an assisting force for Mega Man during times of need.
Proto Man is one of the most powerful characters in the Mega Man universe due to his immense defense capabilities coupled with a formidable offense. Proto Man's signature "weapon" is his shield. Proto Man's shield is large enough to cover the entirety of the front of his body. Made from a unique form of metals, Proto Man's shield is invulnerable to any form of attack. The shield is carried on Proto Man's back, and can easily be utilized for means other than defense (Proto Man is once seen using the shield as a sort of sled/board). Proto Man is also outfitted with a charging buster capable of multiple levels of blast power, his most powerful one being the Blues Big Bang Strike. His ultimate shot being able to destroy a reflective shield wielded by the King Bioroid that was almost as thick as him and parts of the room with it.