Angels Are Functional Beings
Angels are not merely heaven's window dressings. they are functional beings, created to fulfill at least three responsibilities.
We've referred to the angel's most important job, which is to worship God. Isaiah saw the cherubim in the temple who cried out, "Holy, holy, holy, the Lord God of hosts, all the earth is full of his glory" (Isaiah 6:3). Revelation 4:8 says the four living creatures, who are angelic beings, "rested not day and night", to offer God praise and worship.
The fact that Satan sought to rob God of the worship due His name shows that the Devil's basic goal is to distort and corrupt God's plan and replace it with his own system if possible. It makes sense that Satan would attack God's worship first, because the one we worship is usually the one we serve.
That's why Paul warned Timothy about "seducing spirits of error, and doctrines of devils" that will come in the last days. (I Timothy 4:1) Satan's deepest desire is that he be worshiped as God, and to do that he can to distort true doctrine and get people to believe his lies.
The second job of angels is to execute the program of God. To put it another way, angels are God's staff to carry out his will. God manages His universe not as a lone entrepreneur, but as the head of a corporation. God could do it all Himself, but He has chosen to work through His creatures, including both angels and humans. So it's not surprising that we find demons seeking to counter God's program.
The third basic job of angels is the one your are probably most interested in because it affects Christians most directly. Recall that angels are "ministering spirits, sent to minister for them, who shall receive the inheritance of salvation" (Hebrews 1:14)
Therefore, the popular view of angels is less than accurate. These beings don't just show up randomly to pluck people from cliffs or perform other feats. God is using the angels for His kingdom purposes, and if it's not related to the kingdom, then He doesn't send the angels.
Angels minister to the saints (those who are part of Jesus' church in cooperation with the will of God. One of the most dramatic examples of their ministry on behalf of God is the angel that rescued Peter from prison.
What's interesting is that after Peter got out and went to the home of Mary where people were praying for his release, the believers refused to believe God had answered their prayer. "It is his angel," they told the servant girl Rhoda when she kept insisting that Peter was at the door (Acts 12:7-8,15). In other words, there was a belief in the early church that believers had angels assigned to them. It's obvious that Peter did, because his angel showed up and got him out of jail.
God uses angels for kingdom purposes for children as well, even before they know the Lord. One very familiar verse in this regard is Matthew 18:10, where Jesus said of children: "See that you despise not one of these little ones: for I say to you, that their angels in heaven always see the face of my Father who is in heaven."
This is the source of the concept of guardian angels. Why are the angels of theses children looking into the face of God? In the context of Jesus' warning, the angels are waiting for God to tell them what He wants them to do with the person who is messing over His kids. Clearly, children have protective angels.