Definition and Nature:
Angels are spiritual beings created by God to serve as His messengers and to execute His will. They are often depicted as powerful and holy, existing in the heavenly realm. The term "angel" is derived from the Greek word "angelos," meaning "messenger." In the Bible, angels are portrayed as servants of God who carry out His commands and minister to believers.

Biblical Descriptions:
Angels are frequently mentioned throughout the Bible, with their primary role being to serve God and assist in His divine plan. They are described as mighty and numerous, as seen in Revelation 5:11 : "Then I looked, and I heard the voices of many angels and living creatures and elders encircling the throne, and their number was myriads of myriads and thousands of thousands."

Roles and Functions:
1. Messengers of God: Angels often deliver messages from God to humans. For example, the angel Gabriel announced the birth of Jesus to Mary (Luke 1:26-38).

2. Worshipers of God: Angels are depicted as worshiping God continually. In Isaiah 6:3 , the seraphim proclaim, "Holy, holy, holy is the LORD of Hosts; His glory fills the whole earth."

3. Warriors and Protectors: Angels are involved in spiritual warfare and protection. Michael the archangel is described as a warrior in Daniel 10:13 : "But the prince of the kingdom of Persia withstood me for twenty-one days. Then Michael, one of the chief princes, came to help me."

4. Ministers to Believers: Angels are sent to minister to those who will inherit salvation. Hebrews 1:14 states, "Are not the angels ministering spirits sent to serve those who will inherit salvation?"

Hierarchy and Order:
The Bible suggests a hierarchy among angels, with different ranks and orders. Michael is referred to as an archangel, indicating a position of authority (Jude 1:9). Other orders include cherubim and seraphim, each with distinct roles and appearances.

Angelic Appearances:
Angels often appear in human form, though their presence is sometimes accompanied by awe-inspiring phenomena. In Genesis 18, three angels visit Abraham, appearing as men. In contrast, the angelic appearance at Jesus' tomb caused the guards to tremble in fear (Matthew 28:2-4).

Moral and Spiritual Attributes:
Angels are depicted as holy and obedient to God. They are without sin and serve as examples of perfect submission to God's will. However, some angels, led by Satan, rebelled against God and were cast out of heaven (Revelation 12:7-9).

Eschatological Role:
In the end times, angels will play a significant role in God's final judgment and the establishment of His kingdom. They will gather the elect and separate the righteous from the wicked (Matthew 13:41-42).

Significance in Christian Theology:
Angels are integral to understanding the spiritual realm and God's interaction with the world. They exemplify God's power, holiness, and care for humanity. While they are not to be worshiped, as seen in Revelation 22:8-9 , they are respected as God's servants who fulfill His divine purposes.