Angel, from the Greek angelos, meaning messenger, is a supernatural or heavenly being a little higher than man.
Angels are created beings (Ps. 148:2-5, Col. 1:16). Scripture does not tell us the time of their creation, but it was certainly before the creation of man (Job 38:7). They are described as "spirits" (Heb. 1:14). Although without a bodily organism, they have often revealed themselves in bodily form to man. Jesus said that they do not marry and do not die (Luke 20:3436).
They therefore constitute a company, not a race developed from one original pair. Scripture describes them as personal beings, not mere personifications of abstract good and evil.
Although possessed of superhuman intelligence, they are not omniscient (Matt. 24:36; 1 Pet. 1:12); and although stronger than men they are not omnipotent (Ps. 103:20; 2 Pet. 2:11; 2 Thess. 1:7).
They are not glorified human beings but are distinct from man (1 Cor. 6:3; Heb. 1:14). There is a vast multitude of them. John said, "I heard the voice of many angels . . . and the number of them was ten thousand times ten thousand, and thousand of thousands" (Rev. 5:11). They are of various ranks and endowments (Col. 1:16), but only one ---Michael--- is expressly called an archangel in Scripture (Jude 9). This great host of angels, both good and bad, is highly organized (Rom. 8:38; Eph. 1:21, 3:10; Col. 1:16, 2:15).
Angels were created holy (Gen. 1:31; Jude 6), but after a period of probation some fell from their state in innocence (2 Pet 2:4; Jude 6). Scripture is silent regarding the time and cause of their fall, but it is clear that it occurred before the fall of man (for Satan deceived Eve in the Garden of Eden) and that it was due to a deliberate, self determined rebellion against God, as a result of which they lost their original holiness, became corrupt, and were confirmed in evil. Some were "cast down to hell," where they are held in chains until the day of judgment (2 Pet. 2:4); while others were left free, and they oppose the work of God.
The work of the angels is varied. Good angels stand in the presence of God and worship Him (Matt. 18:10; Rev. 5:11; Heb. 1:6). They assist, protect, and deliver God's people (Gen. 19:11; Ps. 91:11; Dan. 3:28, 6:22; Acts 5:19). The author of Hebrews says (1:14), "are they not all ministering spirits, sent forth to minister for them who shall be heirs of salvation?" They sometimes guide God's children, as when one told Philip to go into the desert near Gaza (Acts 8:26), and they bring encouragement, as when one spoke encouragingly to Paul in Corinth (Acts 27:23-24). Sometimes they interpret God's will to men (Dan. 7:16, 10:5,11; Zech. 1:9,13,14,19). They execute God's will towards individuals and nations (Acts 12:23; Gen. 19:12-13; 2 Sam. 24:16; Ezek. 9:2,5,7). God uses them to punish His enemies (2 Kings 19:35; Acts 12:23).
Angels had a large place in the life and ministry of Christ. They made their appearance in connection with His birth to Mary, Joseph, and the shepherds. After the wilderness temptation of Christ they ministered to Him (Matt. 4:11); an angel strengthened Him in the Garden (Luke 22:43); an angel rolled away the stone from the tomb (Matt. 28:2-7); and angels were with Him at the ascension (Acts 1:11).
As for the evil angels, it is clear that their principal purpose is to oppose God and to try to defeat His will and frustrate His plans. The word "Satan" means adversary, and Scripture shows him to be the adversary of both God and man. All of his many other names show his nefarious character.
Evil angels endeavor to separate believers from God (Rom. 8:38). They oppose good angels in their work (Dan. 10:1213). They hinder man's temporal and eternal welfare by a limited control over natural phenomena (Job. 1:12-13,19; 2:7). by inflicting disease (Luke 13:11,16; Acts 10:38; 2 Cor. 12:7), by tempting man to sin (Matt. 4:3; John 13:27; 1 Pet. 5:8), and by spreading false doctrine (1 Kings 22:21-23; 2 Thess. 2:2; 1 Tim. 4:1).
They cannot, however exercise over men any moral power independent of the human will, and whatever power they have is limited by the permissive will of God.
Scripture shows that good angels will continue in the service of God in the future age, while evil angels will have their part in the lake of fire (Matt. 25:41).