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 but occasionally interacting with the earthly realm. The term "angel" is derived from the Greek word "angelos," meaning "messenger."

Biblical Descriptions and Roles
Angels are described throughout the Bible as having various roles and responsibilities. They are often seen worshiping God, delivering messages, providing guidance, and executing judgment. In Hebrews 1:14, angels are described as "ministering spirits sent to serve those who will inherit salvation."

1. Messengers of God: One of the primary roles of angels is to deliver messages from God to humans. For instance, the angel Gabriel announced the birth of John the Baptist to Zechariah (Luke 1:11-20) and the birth of Jesus to Mary (Luke 1:26-38).

2. Worshipers of God: Angels are depicted as worshiping God continually. In Revelation 5:11-12, John describes a vision of countless angels around the throne of God, praising Him with loud voices.

3. Protectors and Guides: Angels are often seen as protectors and guides for believers. Psalm 91:11 states, "For He will command His angels concerning you to guard you in all your ways."

4. Warriors and Executors of Judgment: Angels also serve as warriors and executors of God's judgment. In Revelation 12:7-9, Michael and his angels fight against the dragon, symbolizing the spiritual battle against evil.

5. Ministers to Jesus: Angels ministered to Jesus during His earthly life. After Jesus' temptation in the wilderness, angels came and attended to Him (Matthew 4:11). They were also present at His resurrection, announcing His victory over death (Matthew 28:2-7).

Hierarchy and Types
The Bible suggests a hierarchy among angels, with different types and ranks. The archangel Michael is mentioned as a leader among angels (Jude 1:9). Cherubim and seraphim are specific types of angels with distinct roles. Cherubim are often associated with the presence and glory of God, as seen in Ezekiel 10:1-22. Seraphim are described in Isaiah 6:2-3 as having six wings and continually praising God.

Fallen Angels
The Bible also speaks of angels who rebelled against God, led by Satan. These fallen angels, or demons, are opposed to God's purposes and seek to deceive and destroy. Revelation 12:9 describes Satan as "the great dragon... who leads the whole world astray," and he is cast down to the earth with his angels.

Angelic Appearances
Angels often appear in human form when interacting with people. In Genesis 18, three angels visit Abraham, and he initially perceives them as men. Similarly, Hebrews 13:2 advises believers to show hospitality, as some have "entertained angels without knowing it."

Angels in Eschatology
In eschatological events, angels play significant roles. They are involved in the gathering of the elect (Matthew 24:31), the sounding of trumpets (Revelation 8:6-13), and the execution of God's final judgments (Revelation 16:1).

Conclusion
While angels are powerful and significant in the biblical narrative, they are ultimately servants of God, created to fulfill His purposes and to minister to His creation. Believers are encouraged to focus on God, who commands His angels concerning them, rather than on the angels themselves.