Angels are:-

A. ttendants of Christ (2 Thess. 1:7), their exalted Head (Eph. 1:21; 22; Col. 2:10)
B. ringers of good tidings concerning our salvation (see on Luke 2:14; 24:4; Acts 1:11; 1 Tim. 3:16)
C. horisters of heaven (Luke 15:10; 1 Cor. 13:1; Rev. 5:11, 12)
D. efenders of God’s children (Ps. 34:8; 91:11; Dan. 6:22; 10:10, 13, 20; Matt. 18:10; Acts 5:19; 2 Thess. 1:7–10; Rev. 12:7), though the latter outrank them and will judge them (1 Cor. 6:3; Heb. 1:14)
E. xamples in obedience (Matt. 6:10; 1 Cor. 11:10)
F. riends of the redeemed, constantly watching over them, deeply interested in their salvation, and rendering service to them in every way, also in executing the judgment of God upon the enemy (Matt. 13:41; 25:31, 32; Luke 15:10; 16:22; 1 Cor. 4:9; Gal. 3:19; 2 Thess. 1:7; 1 Peter 1:12; Heb. 1:14; Rev. 20:1–3)

(Hendriksen, on Mt 18:10)