The following is a short list of the capabilities of fallen angels: Physical Visibility: Although fallen angels are spiritual beings, they appear to have the ability to physically appear to people (like their un-fallen counterparts in Genesis 19:1).
Genesis 6 records the activities of the first batch of fallen angels that fell from Heaven.
The sons of God (fallen angels) were able to marry human women (which strongly suggests the women were able to see them) and produced children (which further suggests that fallen angels were able to appear physically to women).(1) And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them, (2) That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose…(4) There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.” (Genesis 6:1-2, 4)Physical Transformation and the Ability to Deceive: 2 Corinthians -15 informs us that Satan’s ministers/fallen angels have the ability to transform themselves so that they can pose as ministers of righteousness.(13) For such ones are false apostles, deceitful workers transforming themselves into apostles of Christ.
(14) And did not Satan marvelously transform himself into an angel of light?
In the King James Version of the Bible demons are referred to as “devils”.