Having a body of flesh and bones is a godly thing. Prior to coming to this earth, there was a war in heaven and Lucifer and his minions chose to rebel against God and were cast out of heaven into this earth and became the devil and his angels (Rev. 12). When they were cast out, they were denied the opportunity to receive bodies of flesh and bones which brings more joy to the spirit of mankind. Because the evil spirits of Lucifer's minions cannot gain a body of flesh and bones, they have been known to try to possess the bodies of those who sided with God the Father and Jesus and who were born with bodies into this life. God the Father and Jesus Christ have immortal resurrected bodies of flesh and bones. They do not possess our bodies. However, as JGalt has mentioned, there is a personage of the Godhead who does not yet have a body of flesh and bones known as the Holy Ghost. It is his mission to touch the souls of mankind and bring them unto God the Father and his Son Jesus Christ. In the Church of Jesus Christ, it has always been a practice to confer the gift of Holy Ghost upon members of Jesus Christ's church through the laying on of hands of those who hold the high priesthood of God. This allows members of Christ's church to have the gift of the Holy Ghost to be with them often. This does not mean that others cannot also be touched by the Holy Ghost for it is his mission to lead all unto God. As also mentioned above, when the Holy Spirit enters into a person, it is a sweet and beautiful experience and it will testify of God the Father and Jesus Christ. Thus it will cause you to believe in God the Father and His Son Jesus Christ.
The advice of the Apostles of Jesus Christ is to try the spirits we come in contact with. Do they bring the belief and love of our Savior Jesus Christ into you? If not, then I warn you not to invite them into your bodies. If so, then you can rest assure that it is from God. If you are ever experiencing a visitation by a spirit, you can test the spirit by offering to shake their hand. If a spirit comes from God and does not yet have a body, they will deliver their message but will not try to shake your hand. If it be a spirit of the devil, he will try to shake your hand but you will not feel it. In this way you can detect him. If it be a messenger from God who does have a body (resurrected or translated), he will shake your hand and you will feel it. It is always a good idea to ask God to protect you from evil spirits that are in the world.