Guts Man is one of Dr. Light's first robots, appearing in the original Mega Man game. His primary means of attacking is shaking the ground by landing (due to his massive size) and throwing Guts Blocks. He gives the ability Super Arm when defeated, and is weak against the Hyper Bomb weapon, obtained from Bomb Man.
Guts Man was intended to help with construction, but when Dr. Wily stole him, he was reprogrammed to do evil deeds.
In Mega Man Powered Up, if played as anyone except Guts Man, the story is the same as the original, but if one plays as Guts Man, everyone is stolen except for Guts Man. He has the ability to make Guts Blocks out of absolutely nothing, and pick them up, just like the original game.
Guts Man is a popular Robot Master, showing up in a variety of bosses in Wily stages.
The first is Mega Man 2, where a Guts Dozer is seen. The Guts Dozer has the upper body of Guts Man, but his legs are a tank. He shoots small pellets out of his mouth, and little Metools shoot out of the main body of the tank
Guts Man makes one real appearance in Mega Man 3 at the end, where all of the original Robot Masters are revealed. Also, the Gamma boss bears resemblance to Guts Man, but only the head part is similar.
He has a big role in Mega Man 7 as a Wily Castle Boss named Guts Man G, a modified version of Guts Man featuring mechanical ligaments, but a similar body type. This was done by Dr. Wily breaking into the Museum of Robots and stealing Guts Man.
Guts Man is also in Mega Man 8, but merely featured in a cameo in the opening video animation.
Guts Man plays a minor part in Super Adventure Rockman, only showing up in the start and when Mega Man is nearly defeated by a Robot Master he faces. He recommends, like his brothers, that Mega Man goes back to Dr. Light's Laboratory. However, if the player chooses this, the game ends with Roll dying and Dr. Wily cackling in triumph over them.
In the Mega Man Battle Network Series, Guts Man is incarnated as GutsMan.EXE, a NetNavi belonging to Dex Oyama, and is an ally of that series' version of Mega Man. He, like his original robot counterpart, is bulky, tough, and intimidating to opponents. His chip given is him breaking the ground in front of him and causing some damage to opponents who are in the way of the big breakage.