ANGELS
All bible quotes are from the Contemporary English Version, unless otherwise noted.

GENERAL INFORMATION

Angels are heavenly sons of God (Job 1:6, Job 38:7, Ps. 89:5-6). The classes of angels are:
Cherubs/Cherubim (Genesis 3:24, Exodus 25:18-20)
Seraphs/Seraphim (Isaiah 6:2,6)
Archangel (1 Thessalonians 4:16, Jude 9)

Only one angel is mentioned by name in canonical scripture: Gabriel (Daniel 8:16, Daniel 9:21, Luke 1:19,26). Only one Archangel is mentioned in canonical scripture, and his name is Michael (Jude 1:9). Other angels refused to give their names when asked (Judges 13:6, 17-18), or were simply not identified by name (Genesis 16:7-11, Exodus 3:2, Numbers 22:22, etc.). There are hundreds of thousands of angels (2 Kings 6:15-17, Matthew 26:53). Angels perform duties assigned to them from God (Genesis 19:1-17, 32:1, Exodus 23:20, Numbers 22:22, 1 Chronicles 21:27, Matthew 4:11, Luke 1:26, Galatians 3:19). Angels were already in existence when the Earth was created (Job 38:1-7). We know angels have free will because they are capable of sin (Genesis 6:1-4, 2 Peter 2:4-5). Angels who commit sin are punished (1 Peter 3:19-20, 2 Peter 2:4, Jude 6).

Angels can communicate with humans in several different ways:
Appearing in human form (Gen 16:7-8, Num 22:31, Judges 6:21, 13:3-6),
As a voice from above (Genesis 21:17, 22:11)
In dreams (Genesis 31:11-12, Matthew 1:20, )
As flames (Exodus 3:2, Exodus 14:24 )
As clouds (Exodus 14:19)
In visions (Acts 10:3)

Angels are mighty creatures who have amazing abilities :
They can become visible at will (Numbers 22:31, Luke 1:11 ).
They can present as regular people (Judges 13:16, Hebrews 13:2 ).
They can defy gravity (Judges 13:19-20).
They can protect large numbers of people (Exodus 23:20)
A single angel can kill large numbers of people simultaneously (2 Kings 19:35).
They have superhuman strength (Matthew 28:2).
They have the power to miraculously heal people (John 5:4).
Angels can unlock prisons (Acts 5:19, 12:7).
They have power over ferocious animals (Daniel 6:22).

GUARDIAN ANGELS

The concept of "Guardian Angels" comes from various scriptures in the bible. The first one is at Matthew 18:10 which states

Don't be cruel to any of these little ones! I promise you that their angels are always with my father in heaven.

A second one, which seems to be aimed at believers in general, is at Hebrews 1:14 as shown

Angels are merely spirits sent to serve people who are going to be saved.

Others can be found at Exodus 23:20, Psalms 34:7, and Psalms 91:11.

Do these passages mean there are angels assigned to each of us to protect us from harm? Only to a certain extent. Realize that these bible passages specify protection for people who fear God -- not just anyone. This is supported in Genesis 19:1-21 when angels were sent to save Lot from God's wrath on Sodom, and later at Genesis 21:17-19 when an angel was sent to save Ishmael from death in the desert. Much later, an angel was also sent to prevent the Egyptian army from killing the Israelites (Exodus 14:19-20, 24-25). In still another case, an angel was sent to protect three faithful men from burning to death (Daniel Chapter 3), and in yet another case, an angel was sent to protect a man from killer lions (Daniel 6:22). It is clear in scripture: Angels are sent to protect the faithful, not just anyone.

Although God sends angels to protect us, we must realize these angels don't protect us if we are doing something reckless or sinful. For example, if we act recklessly by testing God, we will not be protected (Matthew 4:5-7). If we are sinning and get hurt in the process, we will not be protected (Proverbs 22:8, Galatians 6:7-8, Romans 6:23 ). The bible makes it clear that if we make sinful choices, then we deserve the consequences (Proverbs 1:32, 14:12, 16:25).

Therefore, even though angels are assigned to protect faithful believers, they are not assigned to protect us from our own bad judgment or immoral behaviour.

ANGEL WORSHIP

The bible makes it clear that angels are not to be worshipped. This was shown when the apostle John attempted to bow down to an angel at Revelation 19:10

I knelt at the feet of the angel and began to worship him. But the angel said, "Don't do that! I am a servant, just like you and everyone else who tells about Jesus. Don't worship anyone but God. Everyone who tells about Jesus does it by the power of the Spirit."

and at Revelation 22:8-9

8 My name is John, and I am the one who heard and saw these things. Then after I had heard and seen all this, I knelt down and began to worship at the feet of the angel who had shown it to me. 9 But the angel said, Don't do that! I am a servant, just like you. I am the same as a follower or a prophet or anyone else who obeys what is written in this book. God is the one you should worship.

The prohibition against angel worship is also mentioned at Colossians 2:18, which states:

Don't be cheated by people who make a show of acting humble and who worship angels. They brag about seeing visions. But it is all nonsense, because their minds are filled with selfish desires.

The bible makes it clear that God is the only one who is to be given worship as shown at Deuteronomy 10:20. This concept is supported in the New Testament at Matthew 4:10:

Jesus answered, "Go away Satan! The Scriptures say: `Worship the Lord your God and serve only him.' "

CONCLUSION

Summing it all up, angels are mighty spiritual entities at God's service, but are not gods to be worshipped. They can manifest their presence in a variety of ways, they possess magnificent powers, and have the choice of free-will. It is a priviledge to experience a close encounter with an angel of God.