There are demons in this world. They are moving freely everywhere. They are spirits so we cannot see them. They live in different forms because they have the ability to change into any form and acquire any kind of body which they please. This should be the mentality of every christian. We should not live carelessly. They are evil spirits moving around us who are trying to instigate us to do what is not right and to sin against God. We should not follow the wrong instinct in our hearts and trust only the Holy Spirit.
Matthew 8:28-29 (KJV) And when he was come to the other side into the country of the Gergesenes, there met him two possessed with devils, coming out of the tombs, exceeding fierce, so that no man might pass by that way.
And, behold, they cried out, saying, What have we to do with thee, Jesus, thou Son of God? art thou come hither to torment us before the time?
The demons are in existence in the world at the present. They are not bound in hell yet because their time has not come. Their time is coming when they will be bound into hell. For the mean time, they are still freely moving. That is why we are experiencing satanic manifestation everywhere. These demons can take over any form of flesh and exist either as humans or animals. They enter into people and get them possessed. When someone is possessed with demons, he or she will become insane and mentally derailed. Such people lost their senses and become manipulated by the demon.
The people who are going to be free from demonic possession must have the Holy Spirit in their hearts. To be able to have the Holy Spirit in your heart, you must be born again and accept Jesus Christ into your heart.