history of the prayer to St. Michael is fascinating. You can read about it here. Below is a video of the longer prayer, the original one. It is well worth watching/reading. In Hebrew the name Michael means "Who is like God?" and was the war cry of the angels in heaven against the devil and his minions. While the prayer, which was said after mass, was suppressed during the Vatican II era, both Pope John Paul II and Pope Benedict XVI urged Catholics to continue to pray it. And Pope Leo XIII also composed a St. Michael exorcism prayer that can be used by the faithful in their own name. Also, there is a St. Michael Prayer Campaign by Human Life International that prays for the conversion of abortionists. There are numerous apostolates and organizations in the name of St. Michael.