Demons have personalities and purposes. They are the lowest position in Satan's realm. Demons are angels fallen from Heaven (third Heaven). Satan is their leader. 2 Peter 2:4 shows us some angels sinned and were punished.
[2Pe 2:4 NKJV] 4 For if God did not spare the angels who sinned, but cast [them] down to hell and delivered [them] into chains of darkness, to be reserved for judgment;
Demons cannot separate us from the love of God (Rom 8:38-39).
[Rom 8:38-39 NKJV] 38 For I am persuaded that neither death nor life, nor angels nor principalities nor powers, nor things present nor things to come, 39 nor height nor depth, nor any other created thing, shall be able to separate us from the love of God which is in Christ Jesus our Lord.
Demons (and Satan) cannot disobey God's decrees.
2 Corinthians 11:14-15 says that not only does Satan masquerade as an angel of light, but his servants also masquerade as servants of righteousness. Matthew 7:21-23 teaches that even some who are going to Hell, whom Jesus never knew, at least thought that they had cast out demons.
[2Co 11:14-15 NKJV] 14 And no wonder! For Satan himself transforms himself into an angel of light. 15 Therefore [it is] no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works.
[Mat 7:21-23 NKJV] 21 "Not everyone who says to Me, 'Lord, Lord,' shall enter the kingdom of heaven, but he who does the will of My Father in heaven. 22 "Many will say to Me in that day, 'Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name?' 23 "And then I will declare to them, 'I never knew you; depart from Me, you who practice lawlessness!'
But if people could be deceived, how can any of us know whether or not we are deceived? 2 Thess 2:10-11 give one way. It says they were deceived because they refused to love the truth, but instead have delighted in wickedness.
[2Th 2:10-11 NKJV] 10 and with all unrighteous deception among those who perish, because they did not receive the love of the truth, that they might be saved. 11 And for this reason God will send them strong delusion, that they should believe the lie,
Beelzebub was a demon the Jews accused Jesus of serving (Mt 10:25; 12:24-27; Mk 3:22; Lk 11:15-19). Rather, Baal meant "lord" and zebub means "flies". In the Canaanite and Ugaritic religions there was a lord of this, and a lord of that, and often a high god just called Baal. Zebub means flies, and so the name was calling the idol lord of the flies. 2 Ki 1:2-6,13 speaks of Baalzebub, god of the Philistine city of Ekron.
Then the devil took Him up into the holy city, set Him on the pinnacle of the temple, and said to Him, "If You are the Son of God, throw Yourself down. For it is written:
'He shall give His angels charge over you,'
'In their hands they shall bear you up,
Lest you dash your foot against a stone.'" (Matthew 4:5-6)
The early church was well familiar with demon possession and exorcism; 13 pre-Nicene writers taught about it. Likewise the Bible has many verses about demon possession
An evil spirit tormented Saul in 1 Sam 16:14-23; 18:10; 19:9. It made him try to kill David, and David had to flee for his life.
In Mt 9:32-34 a demon made a man mute
In Mt 12:22,28 Jesus drove out a demon who made a man blind and mute.
In Mt 15:22; Mk 7:26-30 a demon possessed a Syro-Phoenician / Canaanite woman’s daughter
In Mk 1:23; Lk 4:33-36 a demon-possessed man who asked Jesus what He had to do with them.
In Mk 9:14-27 a demon possessed boy would foam at the mouth, gnash his teeth, and become rigid.
Jesus drove out many demons in Mt 8:16; Mk 1:32-39; Lk 6:18; 7:21
More than one demon can be inside a person; Jesus had driven seven demons out of Mary Magdalene (Lk 8:2b; Mk 16:9). There was a legion of demons in the Gerasene demoniac in Mk 5:2-17; Lk 8:27-38.
One likely cause of some demon possession is dabbling in the occult, such as séances, Ouija boards, tarot cards, and fortune telling.
Christians have Authority Over Demons
Jesus rebuked an evil spirit in Lk 9:42 and drove out demons in Lk 13:32. Likewise Christians can cast out demons in Christ’s name (Mt 10:8; Mk 3:15; 6:7,13; 16:17; Lk 9:1; 10:17; Acts 8:7). Someone was driving out demons who was not known to Jesus’ disciples, and Jesus said not to forbid that (Mk 9:38; Lk 9:49).
Now when He rose early on the first day of the week, He appeared first to Mary Magdalene, out of whom He had cast seven demons. (Mark 16:9)
When an unclean spirit goes out of a man, he goes through dry places, seeking rest, and finds none. Then he says, "I wll return to my house from which I came." And when he comes, he finds it empty, swept, and put in order. Then he goes and takes with him seven other spirits more wicked than himself, and they enter and dwell there; and the last state of that man is worse than the first. (Matthew 12:43-45)
The Gospels of Matthew (8:29), Mark (1:24), and Luke (8:30) repeatedly present illustrations of this, as does the book of Acts (19:15).
[The demon said] "Let us alone! What have we to do with You, Jesus of Nazareth? Did You come to destroy us? I know who You are - the Holy One from God!" (Mark 1:24)
Then He [Jesus] asked the him [the demon], "What is your name?" And he answered, saying, "My name is Legion; for we are many." (Mark 5:9)
You believe that there is one God. You do well. Even the demons believe - and tremble! (James 2:19)
And he [the demon] cried out with a loud voice and said, "What have I to do with You, Jesus, Son of the Most High God? I implore You by God that You do not torment me." (Mark 5:7)
I do not want you to have fellowship with demons. You cannot drink the cup of the Lord and the cup of demons; you cannot partake of the Lord's Table and of the table of demons. (1 Cor 10:20-21)
Now the Spirit expressly says that in latter times some will depart from the faith, giving heed to deceiving spirits and doctrines of demons. (1 Timothy 4:1)
1 Tim 4:1 specifically mentions doctrines of demons, and two examples given in 1 Timothy 4:3 are forbidding people to marry, and abstaining from certain foods. Also, even sincere religious sacrifices to idols are for demons and not for God (1 Cor 10:19-21; Dt 32:17). Participating in idol ceremonies is like taking the cup of demons, as opposed to the Lord’s Supper (1 Cor 10:21).
So the demons begged Him [Jesus], saying, "If You cast us out, permit us to go away into the herd of swine." (Matt 8:31)
Then the man in whom the evil spirit was leaped on them, overpowered them, and prevailed against them, so that they fled out of that house naked and wounded. (Acts 19:16)
For they are the spirits of devils, working miracles, which go forth unto the kings of the earth and of the whole world. (Rev 16:14)
Question: "Do demons exist?"
Answer: The Bible speaks of demons as real, actual beings. However, Scripture’s depiction of demons is very different from the popular concept of them. The Bible describes demons as powerful but limited and ultimately defeated creatures. They are angels who followed Satan in rebellion against God (Revelation 12:3–4). The Bible doesn’t give many details about demons, but what it provides is enough to dispel typical myths.
Demons are referred to by several alternate names, including “unclean spirits” and “evil spirits.” Some of the false gods that received human sacrifices are described as actual demons (2 Chronicles 11:15; Deuteronomy 32:17). Since demons are fallen angels, they possess the same level of power and influence as angels. However, Scripture seems to indicate that God has limited their abilities (2 Thessalonians 2:6–7). The Bible indicates that not all afflictions are due to demonic influence (Matthew 10:1; Luke 8:2). The vast majority of demonic influence is spiritual, not physical.
Popular culture frequently depicts demons in monstrous form. This includes drooling fangs, sharp claws, leathery wings, and so forth. Or they are portrayed as shadows or ghosts. None of these have any biblical basis at all. In fact, the Bible never physically describes any fallen angel. As is the case with angels, demons are spiritual creatures with a primarily spiritual influence, so they are unlikely to have any set physical appearance. If they choose to take on a physical appearance, it actually makes more sense for them to choose something inviting rather than scary (2 Corinthians 11:14).
So, demons are literal, actual beings. The demons described in the Bible exist. However, the oft-portrayed horror-movie and Halloween versions do not.