On June 18th, 1961, Saint Michael the Archangel appeared to the girls in Garabandal for the first time. After this, he appeared to them for several days to prepare them for Our Lady's visit.
Saint Michael is one of the seven archangels and is one of the three whose names appear in the Bible. The other two are Gabriel and Rafael. In the Bible, Saint Michael is seen as the great defender of the people of God against the devil. We can pray to Saint Michael the Archangel asking him to protect us from the temptations of the devil and to help us to not fall into sin.