Noah and the Flood, pgs 1-2; “Few men in any age were as great as Noah. In many respects he was like Adam, the first man. Both had served as ministering angels in the presence of God even after their mortal experience. Adam was Michael, the archangel, but Noah was Gabriel, one of those nearest to God. Of all the hosts of heaven, he was chosen to open the Christian era by announcing to Mary that she would become the mother of the Savior, Jesus Christ. He even designated the name by which the Redeemer should be known here on earth, saying He would be the Son of God….” – Mark E. Petersen, Apostle
Luke 1:26; “And in the sixth month the angel Gabriel was sent from God unto a city of Galilee, named Nazareth.”
Angels are mentioned at least 108 times in the OT and 165 times in the NT (Chafer, Systematic Theology, II, 3). Angels aren’t glorified human beings, nor do they have the ability to morph themselves into something else. They were created by God for a number of different functions in which they serve Him.
The Bible explicitly says they don’t marry or reproduce like humans do – Matthew 22:30 – and are here as ministering spirits – Hebrews 1:14. They can take on the appearance of humans – Hebrews 13:2 – and in fact most of the times humans have interacted with them they’ve appeared in human form.
A great article can be read at ChristianAnswers.net that gives one of the most detailed accounts of angels I’ve read in a long time.
Another great resource of reliable information is David Jeremiah’s book “What the Bible says about Angels”.