Can angels and/or demons make themselves appear visibly human (or other physical life form)? Can people be influenced or even possessed by demons and yet act completely normal and be nice and kind to others? Perhaps even praise the Lord? Or do they always do and/or say weird or unusual things?
It is concluded that, since the symptoms of the affliction were frequently those of bodily disease. The New Testament gives a number illustrations of people who were possessed by demons: Dumbness -Matt 9:32, blindness - Mt 12:22, epilepsy - Mr 9:17-27, or those seen in cases of ordinary insanity (as ill) Mt 8:28; Mr 5:1-5. Demoniacs are distinguished from those afflicted with normal bodily sickness - Mat. 4:24, 17:15; Mr 1:32; 16:17-18; Lu 6:17-18.. Demons are represented as speaking in their own persons with superhuman knowledge. Mt 8:29; Mr 1:24; 5:7; Lu 4:41. Demons have power that comes from Satan and twice Jesus distinctly connects demoniacal possession with the power of the evil one -Luke 10:18. At Gardarenes Jesus spoke to and cast out many demons from the maniac of Gardara, ( Mark 5:10-14) and sent them into a herd of swine. Thus the New Testament teaches that there are evil spirits, subjects of the evil one, who, in the days of the Lord himself and his apostles especially, were permitted by God to exercise a direct influence over the souls and bodies of certain men.
Judas was possessed by a devil and betrayed the Lord Jesus- John 13:2, 27, 6:70; Luke 22:3, 31. These demon did not take on human form, but possessed a human who was susceptible to them. Believers cannot be possessed by demons and they are indwelt by the Holy Spirit. The devil can influence weak and unfaithful Christians. Satan and his demons can do nothing the Lord does not allow them to do - See Job 1-2.
There many people who are under the influence of Satan and some who are demon possessed. However, one should be careful in not assuming demon possession of people who simply have serious diseases. Mental illness should not be assumed to be caused by demon possession. Further, man has a sinful nature and can do all sorts of evil without being demon possessed. A man can be “two faced” and a hypocrite being unsaved and yielding to his carnal nature.
A number of times in the Old Testament angels appeared as men being messengers from God. (See Gen. 19:1) The is no example of angels appearing to men after the Jews rejected Jesus and the Gospel went to the Gentiles. Angels will be very active in the coming seven year Tribulation period when God again begins to work with the Nation of Israel.