The Bible reflects God’s knowledge of the universe rather than man’s; therefore, in the Scriptures, the angels, concerning whom man of himself could know nothing, are introduced with perfect freedom, being mentioned about one hundred and eight times in the Old Testament and one hundred and sixty-five times in the New Testament.
The word angel means messenger, and in its Biblical use is sometimes employed of God, when as the Angel of IHVH (Jehovah or Yahweh), He Himself serves as a messenger to men (Gen. 16:1-13; 21:17-19; 22:11-16); it is used of men (Luke7:24; Jas. 2:25; Rev1:20; 2:1,8,12,18;3:1,7,14); and of departed spirits of men (Matt18:10; Acts12:15). Of the latter use of the word it should be noted that, though the departed spirits of men may be called angels, the angels are not departed spirits of men, nor do men at death become angels.

The angels are a distinct order of creation and have been given a heavenly position, or sphere, above the sphere of man (Ps8:5; Heb2:7; Rev5:11; 7:11). Three heavens are mentioned in the New Testament (first heaven is where birds fly, or ”sky” Gen1:20, second heavens is the universe with its stars Ps19:1, and the third heaven is the habitation of God, beyond the material universe 2Cor12:2), and in the Old Testament the word heaven is plural. When entering the human sphere, Christ was thereby, for a little time made lower than the angels (Heb2:9); when returning to Heaven, Christ again passed through the angelic sphere (Heb4:14; 9:24) and was seated far above principalities and powers (Eph1:20, 21).
Since we know that there are many forms of created beings of a lower sphere than man, it is reasonable to believe that, though invisible, there are beings of a higher order than man. Like all beings, other than the Godhead, the angels are created. In Colossians 1:16 mention is made of their creation, and in Ez28:13,15, the creation of Satan — one of the angelic order — is mentioned in particular.
The angels are always referred to in the masculine gender, and as to their number we read of “an innumerable company” (Heb12:22, which word should be translated “myriads.” Note Matt26:53; Dan7:10; Rev5:11). It is also implied that there is no increase of their number by generation (Matt22:30) and we know of no cessation of their existence by death.
If the angels have bodies, their bodies are of a spiritual order (1Cor15:44). When seen of men they have, for the time being, a material appearance (Matt28:3;Rev15:6;18:1). On the other hand, those of the angelic company known as demons are seen to be seeking entrance into the bodies of the creatures of earth (Luke11:24-26).
Two classes of angelic beings are to be distinguished:

1. Their nature. The unfallen angels are the “ministering spirits” (Heb1:14) who kept their first estate and are therefore designated as the “holy angels” (Matt25:31). In the Scriptures, these are in view in almost every reference to the angels. Of the holy angels, several are mentioned in particular as well as certain classes:
(1) Michael the Archangel, whose name means “who is like unto God” (Dan10:21; 12:1; Jude1:9; Rev12:7-10).
(2) Gabriel, whose name means “the mighty one,” and to whom has been entrusted various heavenly messages (Dan8:16; 9:21; Luke1:19, 26-38).
(3) The Elect Angels (1Tim5:21).
(4) Principalities and Powers, which term is sometimes used of all angels, and sometimes of only the fallen angels (Rom8:38; Eph1:21; 3:10; Col1:16; 2:10, 15; 1Pet3:22; Luke21:26).
(5) Cherubim, or living creatures, who defend God’s holiness from the pollution of sinful beings (Gen3:24; Ex25:17-20; Ez1:1-18. Note also the original purpose for which Satan was created, Ez28:14).
(6) Seraphim (Is6:2-7).
(7) The Angel of Jehovah, which title belongs only to God and is used in connection with the divine manifestations in the earth and therefore is in no way to be included in the angelic hosts (Gen.18:1 to 19:29; 22:11,12;31:11-13;48:15,16;32:24-32; Josh5:13-15; Judg13:19-22; 2Kings19:35; 1Chron21:12-30;Ps34:7). The strongest contrasts between Christ, who is the Angel of Jehovah, and the angelic beings is presented in Hebrews 1:4-14.
2. Their ministry. Of the ministry of the unfallen angels revelation declares:
(1) They were present at creation (Job38:7), at the giving of the law (Gal3:19; Acts7:53; Heb2:2; Rev22:16), at the birth of Christ (Luke2:13), at the temptation (Matt4:11), in the garden (Luke22:43), at the resurrection (Matt28:2), at the ascension (Acts1:10), and they will yet appear at the second coming of Christ (Matt24:31; 25:31; 2Thess1:7).
(2) The angels are ministering spirits sent forth to minister to those who shall be heirs of salvation (Heb1:14; Ps34:7;91:11). Though we have been given no communication or fellowship with the angels, yet we should recognize the fact of their ministry which is constant and effective.
Man is forbidden to pray to the angels or to worship them Rev19:10, 22:8. Angels cannot be mediators between God and man, but Jesus who is God and man at the same time, Jesus is the only mediator 1Tim2:5. Angels are only as soldiers sent by their commander to do missions: you don’t approach a soldier with a request but their commander, which is Jesus, Lord of Hosts Rev19:11-20.
(3) The angels are spectators and witnesses of the things of earth (Ps103:20; Luke12:8, 9; 15:10; 1Cor11:10; 1Tim3:16; 1 Pet1:12; Rev14:10).
(4) Lazarus was carried by the angels to Abraham’s bosom (Luke16:22).

The fallen angels have been divided into two classes: (1) those that are free and (2) those that are bound. Of the fallen angels, Satan alone is given particular mention in the Scriptures.
When Satan fell (John 8:44) he drew after him a multitude of lesser beings Rev12:4. Of these, some are reserved in chains unto judgment (2Pet 2:4; Jude1:6; 1Cor6:3); the remainder are free and are the demons, or devils, to whom reference is constantly made throughout the New Testament (Mark5:9, 15; Luke8:30; 1Tim4:1). They are Satan’s aids in all his undertakings and share his doom (Matt25:41; Rev20:10).