Debuting in the original Mega Man, he was built by Dr. Light (with Dr. Wily according to some sources) to help with construction work, along with Bomb Man. With his Super Arm, he is capable of lifting and transporting heavy boulders, among other things.
Dr. Wily built a huge tank with his form in Mega Man 2, Guts-Dozer, and again as a drilling machine in Mega Man 7, Guts Man G. There are also other robots that are similar to him, like Guts Hover, Gamma and Gorisly. He and Stone Man are good friends.
Though Guts Man is considered stupid (mostly because of his cartoon version), in Mega Man Powered Up it is shown that he has average intelligence.
Mega Man Megamix Vol. 1 profile
"Guts Man, who was designed to form and develop the land, was given superhuman strength to perform his duties. A lot of time was spent reinforcing Guts Man's joints so that they could withstand the strain of constant heavy lifting. Covering his entire outer shell with Ceramic Chitin resulted in a larger physical form, but since he was expected to be working only under the safest of circumstances, less attention was paid to reinforcing the sensitive electronics contained within his body, and they are vulnerable to heavy impacts like those from exploding Hyper Bombs. Despite his extreme strength, Guts Man has a kind and gentle personality."