What are angels?
There is a lot of speculation about angels in modern culture. Christmas is a good time to reflect on their role in God's Kingdom.
While there are a lot of references to them (more on on that below), no section of Scripture treats them in detail. Still there are enough incidental details to furnish us with lots of intel on them.
Theologians have tried to analyze the names as different categories of angels, but no one really agrees on how to do that or if we should bother. They are spoken of as of different ranks in dignity and power (Zech. 1:9, 11; Dan. 10:13; 12:1; 1 Thess. 4:16; Jude 1:9; Eph. 1:21; Col. 1:16). Two of them have names: Gabriel (Dan 8,9; Luke 1) and Michael (Dan 10; Jude 9; Rev 21).
The term “angel” shows us 203 times in the Bible. The Greek word angelos sometimes refers to human messengers. For example, this is probably what’s happening in Revelation 2 where the angels to the seven churches is probably a reference to their pastors. But I’ll stick to the non-human kind.
First, their name. The primary Hebrew word for angel, “malawk” means deputy or ambassador. Greek angelos means herald or messenger. They are also called “Living creatures” (Ezek 1:5), “cherubim” (Gen 3:24, Ex 25:18ff etc), “seraphim” (Isa 6:2,6), “sons of God” (Job 1:6, etc) “sons of the mighty” (Ps 29:1, etc) “spirits” (1 Kings 22:9, etc), “holy ones” (Deut 33:2-3, etc), “watchers” (Dan 4:13, etc), “principalities and powers” (Romans 8, Eph 6, etc), “thrones” (Col 1:16). And my personal favorite where in 2 Kings 6:17 they are evidently drivers of “horses and chariots of fire.” How’d that look on your LinkedIn profile?
Secondly, there are lot of them. Called “hosts” (Luke 2:13), “camp” (Gen 32), “legion” (Matt 26). “Thousand of thousands” (Dan. 7:10; Matt. 26:53; Luke 2:13; Heb. 12:22, 23).
Thirdly, as to their nature. they have a different nature than we do, although they are similar in some ways. As to their nature, they are spirits (Heb. 1:14) and yet they take on human form (Gen. 18:2; 19:1, 10; Luke 24:4; Acts 1:10). Like us they are creatures (Job 4:18; Matt. 24:36; 1 Pet. 1:12). As finite creatures like us they may fall under temptation; and so we read of “fallen angels.” Of the cause and manner of their “fall” we do not know but that hasn’t stopped people from creating cottage industries on the subject. Unlike us, angels never die (Luke 20:36). They are possessed of superhuman intelligence and power (Mark 13:32; 2 Thess. 1:7; Ps. 103:20). They are called “holy” (Luke 9:26) -- something we are now in part. They are called “elect” (1 Tim. 5:21). The redeemed in glory are “like unto the angels” (Luke 20:36).
Fourthly, as to their function. In the widest sense they are agents of God’s providence (Ex. 12:23; Ps. 104:4; Heb. 11:28; 1 Cor. 10:10; 2 Sam. 24:16; 1 Chr. 21:16; 2 Kings 19:35; Acts 12:23). They are specially God’s agents in carrying on his great work of redemption.
Fifthly, their workload. From the time of Abraham onward there are frequent references to their ministry on earth (Gen. 18; 19; 24:7, 40; 28:12; 32:1). They rebuke idolatry (Judg. 2:1–4), call Gideon (Judg. 6:11, 12), consecrate Samson (13:3), for example.
The Incarnation introduces a new era in the ministrations of angels. They predict his advent (Matt. 1:20; Luke 1:26–38), minister to him after his temptation and agony (Matt. 4:11; Luke 22:43), and declare his resurrection and ascension (Matt. 28:2–8; John 20:12, 13; Acts 1:10, 11).
Today, they are now ministering spirits to the people of God (Heb. 1:14; Ps. 34:7; 91:11; Matt. 18:10; Acts 5:19; 8:26; 10:3; 12:7; 27:23). They rejoice over a penitent sinner (Luke 15:10). They bear the souls of the redeemed to paradise (Luke 16:22); and they will be the ministers of judgement hereafter on the great day (Matt. 13:39, 41, 49; 16:27; 24:31). The passages (Ps. 34:7, Matt. 18:10) usually referred to in support of the idea that every individual has a particular guardian angel have no such meaning. They merely indicate that God employs the ministry of angels to deliver his people from affliction and danger, and that the angels do not think it below their dignity to minister even to children and to the least among Christ’s disciples.
Sixth, they are not to be worshipped. Angels are so great in number and so powerful that human beings are sometimes tempted to worship them (Col. 2:18; Rev. 19:10). . John fell down to worship at an angels feet but the angel rebuked him. So, artists have often pictured angels as superior to men, flying in the clouds, but Scripture teaches us that their superiority over us is only temporary. Human beings, not angels are made in then image of God (Gen 1). And the world to come belongs to men and not to angels. “What is man that you are mindful of him, or the son of man, that you care for him? You made him for a little while lower than the angels; you have crowned him with glory and honor, putting everything in subjection under his feet” (Heb 2:5-6). Through the work of Jesus we will actually rise above the angels. 1 Corinthians 6:3 Paul says without explanation, “Do you not know that we are to judge angels?”
Ephesians 3:10 and 1 Peter 1:12 presents angels as spectators to the drama of human salvation. Amazingly, it is we, the church, who teach angels.  To me, though I am the very least of all the saints, this grace was given, to preach to the Gentiles the unsearchable riches of Christ,  and to bring to light for everyone what is the plan of the mystery hidden for ages in God, who created all things,  so that through the church the manifold wisdom of God might now be made known to the rulers and authorities in the heavenly places.
The longing of Angels includes a holy curiosity to watch and delight in the glories of Christ’s kingdom as they find ever fuller realization in the lives of individual Christians throughout the history of the church (cf. Eph 3:8-10).
Angels wait for the redemption of the entire creation (Rom 8:19) and they rejoice over the sinner’s repentance (Lk 15:10) and join in the concert of praise at the consummation of redemption (Rev 5:11-14, 19ff).What the prophets prophesied and what the angels long for -- namely, the realization of salvation from God -- has become reality for any here who believe.
In summary, the angels are created intelligent beings who adore God through their callings as they bring God’s word, fight God’s battle, and minister to God’s people.
More reading: Systematic Theology. John Frame, Systematic Theology, 771-775.