Megaman is the Net-Navi of Lan Hikari and was created by Lan Hikari's father.  It was shown later in the manga that he was actually the reincarnation of Lan's twin brother Hub. This is said to be the reason why they are able to synchronize with each other both physically and mentally. The two developed a strong friendship and have had a sort of love-hate relationship. 
He is a very social Net-Navi and he tries to keep the peace when he is with his friends Roll, Gutsman, and Glide. These Net-Navis are the Net-Navis of Lan's friends Mayl, Dex, and Yai.
He has gone through many changes while fighting to keep the Net safe from evil. He obtained the ability of style-change from Dr. Hikari, which allows him to become any elemental-type Net-Navi he wants. Later on, he becomes able to unite with his friends' souls to become to take on their abilities and part of their appearance.