Unlike the various theophanies, I am unable to pick the most important Ministration of Angels.
God sends angels to men for very specific, important, and essential reasons.
Each manifestation or ministration of an angel is just as important as any other, to accomplish the purposes of God.
God sends a messenger from Heaven to accomplish a specific mission or goal. Messengers from the Father deliver messages to men and women, and thus further the purposes of God.
The thing you have to be careful about is the fact that Satan also sends messengers and also appears as an angel of light, from time to time. Therefore, we have to learn to discern the difference between a messenger from God and a messenger from Satan.
Messengers from God will build up the Church and Kingdom and Gospel of Christ, the Church of Jesus Christ in any Gospel Dispensation or any time period. Messengers from Satan will try to find some way to tear it all down.
Study each and every Gospel Dispensation. You will soon see that God sent angels or messengers to establish and sustain each Gospel Dispensation and the mortal prophet that God called to lead that particular Gospel Dispensation. It should be no surprise that the greatest heavenly manifestations will always be given to the Head of a Gospel Dispensation. The Dispensation Head is chosen to represent God and His Priesthood here on earth.
Angels from God reveals God’s will to the world.