Saint Michael the Archangel isn't a saint, but rather he is an angel, and the leader of all angels and of the army of God. This is what the title "Archangel" means, that he is above all the others in rank.
St. Michael has four main responsibilities or offices, as we know from scripture and Christian tradition.
Today, St. Michel is invoked for protection, especially from lethal enemies. He is also the patron of soldiers, police and doctors.