The appearance of angels was not an uncommon occurrence in the book of Acts.
As Christians, we too should not shy away from the fact that God sometimes sends angels to minister to us.
Hebrews 1:13-14 To which of the angels did God ever say, " Sit at my right hand until I make your enemies a footstool for your feet"?
Are not all angels ministering spirits sent to serve those who will inherit salvation? (NIV)
The first record of angels in the Acts of the Apostles appears in Acts 1:10. Although the two men here are not called angels it is quite evident that they are. They brought words of comfort and encouragement to the bewildered disciples who were seeing Jesus go for the second time.
Release from prison
Acts 5:17-21 brings us the amazing story of the release of the Apostles from prison by an angel. The angel also told them to go to the temple and speak the words of life. This is a common message that angels bring.
This was not the only time we see angels releasing people from prison. In Acts 12:1-19 we witness an angel releasing Peter from prison. You will notice that it is almost an effortless task for the angel. The soldiers guarding Peter seemed not to exist. They must have been "like dead men" Matthew 28: 1-4. Even the Iron Gate opened without any effort.
Acts 16:25-34 records another release from jail for Paul and Silas, although an angel is not mentioned you can see the finger marks of one all over the place.
Bring clear direction and guidance
Acts 8:26 shows us another ministry of angels. We see Philip the evangelist receiving direction and guidance from an angel. The result is that the eunuch is saved.
The same thing happens with Acts 10:3-6 and Cornelius gets saved. Angels are not limited in who they can appear to. Cornelius saw an angel before becoming a Christian.
Acts 27:23-38 also records an angel appearing to Paul. Paul goes on to give the direction and guidance he received from the angel to the men in the ship.
Instruments of God's judgement
Acts 12:20-25 records an angel striking Herod dead. Angels are God's servants carrying out His will at His command.
Duties of Angels
Angels carry out our heavenly father's orders. They minister to us. No where are we told in scripture to pray to angels or order them about. God orders them. We are to pray to God in Jesus name. It is up to God to send one of his angels to work on our behalf if He so pleases. A good example of this is when Herod took James and God allowed him to be killed. When Peter was arrested God sent an angel to rescue him. It is God's prerogative (Acts 12:1-13)
Other facts we can learn about angels in the scriptures are
Testimony about angels