The English word angel, as used in the New Testament, comes from the Greek word angelos meaning "a messenger". thus it is not surprising that this is precisely what we find angels doing in the Bible.
The angel Gabriel is mentioned four times in the Bible, twice in Daniel and twice in Luke.
15And it came to pass, when I, even I Daniel, had seen the vision, and sought for the meaning, then, behold, there stood before me as the appearance of a man. 16And I heard a man's voice between the banks of Ulai, which called, and said, Gabriel, make this man to understand the vision. 17So he came near where I stood: and when he came, I was afraid, and fell upon my face: but he said unto me, Understand, O son of man: for at the time of the end shall be the vision.
20And whiles I was speaking, and praying, and confessing my sin and the sin of my people Israel, and presenting my supplication before the LORD my God for the holy mountain of my God; 21Yea, whiles I was speaking in prayer, even the man Gabriel, whom I had seen in the vision at the beginning, being caused to fly swiftly, touched me about the time of the evening oblation. 22And he informed me, and talked with me, and said, O Daniel, I am now come forth to give thee skill and understanding. 23At the beginning of thy supplications the commandment came forth, and I am come to shew thee; for thou art greatly beloved: therefore understand the matter, and consider the vision. 24Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy. 25Know therefore and understand, that from the going forth of the commandment to restore and to build Jerusalem unto the Messiah the Prince shall be seven weeks, and threescore and two weeks: the street shall be built again, and the wall, even in troublous times. 26And after threescore and two weeks shall Messiah be cut off, but not for himself: and the people of the prince that shall come shall destroy the city and the sanctuary; and the end thereof shall be with a flood, and unto the end of the war desolations are determined. 27And he shall confirm the covenant with many for one week: and in the midst of the week he shall cause the sacrifice and the oblation to cease, and for the overspreading of abominations he shall make it desolate, even until the consummation, and that determined shall be poured upon the desolate. 19And the angel answering said unto him, I am Gabriel, that stand in the presence of God; and am sent to speak unto thee, and to shew thee these glad tidings. 26And in the sixth month the angel Gabriel was sent from God unto a city of Galilee, named Nazareth, 27To a virgin espoused to a man whose name was Joseph, of the house of David; and the virgin's name was Mary. 28And the angel came in unto her, and said, Hail, thou that art highly favoured, the Lord is with thee: blessed art thou among women. 29And when she saw him, she was troubled at his saying, and cast in her mind what manner of salutation this should be. 30And the angel said unto her, Fear not, Mary: for thou hast found favour with God. 31And, behold, thou shalt conceive in thy womb, and bring forth a son, and shalt call his name JESUS. 32He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David: 33And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end.
While all angels are messengers, the angel Gabriel seems particularly to have had a ministry connected with the Messiah, Jesus Christ, as the messages delivered mostly relate to Him.