Not much is known about the Man of Iron. He has a tendency to shoot first then ask no questions afterward, but he is loyal and will carry out his mission even if it takes eons. He got his moniker from the local inhabitants of the planet he was on. He is the stuff of legends. Literally.
Marvel UK comics
The Man of Iron and Navigator were on a rescue mission from Cybertron. They were sent to search for the Ark and her lost crew. They tracked the Ark to Earth but could not find them buried under Mount St. Hilary. Navigator lay dormant inside their rescue craft that was buried underground, in England but the Man of Iron would periodically go to the surface to have a look around. These appearances spooked the humans living there, spawning local legends of the "Man of Iron" that were passed down through the centuries. While roaming around, the Man of Iron showed little interest in communicating with the men there, and would not hesitate to open fire on them if he thought they were threatening.
The rescue craft sent out a beacon hoping to attract the attention of those lost on the Ark. It was indeed successful in attracting the attention of both the Autobots and Decepticons, who were newly reactivated after Mt. St. Hilary erupted. The Man of Iron appeared once again only to lose a firefight with Thundercracker. Or Skywarp. Or possibly even Starscream. Accounts vary on the subject.
The Man of Iron and his Navigator both share nearly identical character models, differentiated only by their heads. Their robot forms are highly genericized, lacking any distinguishing features that would hint at what their vehicle mode is, if any.