Although the Bible mentions angels over 250 times, the references are usually incidental to some other topic. Learning what the Bible has to say about angels can certainly aid in an understanding of God and His ways, but what is learned about the angels themselves must usually be drawn from implicit, rather than explicit, descriptions.
Angels are spiritual beings who have personalities that include emotions (Luke 2:13–14), intelligence (2 Corinthians 11:3, 14), and wills (2 Timothy 2:26). Satan was an angel who was cast out of heaven along with many other angels who decided to follow him and chose to sin (2 Peter 2:4). Satan’s will is mentioned directly in 2 Timothy 2:26. The Bible speaks of demons who, by their own choice, “did not keep their positions of authority but abandoned their proper dwelling” (Jude 1:6). Demons demonstrate their free will in several passages of Scripture. Legion chose a herd of pigs as their destination (Luke 8:32). In Micaiah’s vision of God’s throne room, God allows a spirit to choose how to bring ruin upon King Ahab (1 Kings 22:19–22).
Before some of the angels exercised their free will to rebel against God, they could have been in a sort of “probation period,” similar to Adam and Eve’s time in the garden. Those angels who did not choose to sin and follow Satan have become the “elect” angels (1 Timothy 5:21), confirmed in holiness. These angels are also referred to as “holy angels” (Mark 8:38) and “holy ones” (Psalm 89:5). Those angels who did choose to sin in siding with Satan have become the “unclean spirits” (Mark 1:23) or demons.
Even if the elect angels are confirmed in their holiness, it doesn’t mean they have lost their free will. Certainly, every living creature has choices to make at any given moment. It’s possible that the holy angels still have the ability to sin, but that does not mean that they will sin. Being holy angels, they always do God’s bidding. Being volitional creatures, the elect angels have a desire to praise and serve God, and they choose to do so. God’s will always matches their own will.
Humans have free will, but they struggle with sin because the human nature has been corrupted by sin. This is why all humans sin (Romans 5:12) and find it much more difficult to “be good” than to “be bad.” The holy angels are without a sinful nature. They are not inclined toward sin but rather toward righteousness, doing everything that pleases God.
In conclusion, the holy angels have a free will, but the Bible makes it clear that they do not sin in their service to God. The apostle John, in describing the eternal state, wrote there will be no mourning, crying, or pain in that place and time (Revelation 21:4), and anyone who does evil will never be permitted to enter the city of God (Revelation 21:27). The angels who are present in that holy city are therefore sinless.