Angels and jinn can assume different forms and shapes and appear in this world. Here, we observe movement from the visible to the invisible: Water evaporates and disappears into the atmosphere, solid matter becomes a liquid or a gas (steam), and matter becomes energy (nuclear fission). Likewise, we observe movement from the invisible to the visible: Gases become fluids, evaporated water becomes rain (as well as snow or hail), and energy becomes matter. Similarly, intangible thoughts and meanings in our minds can appear in the tangible form of letters and words in essays and books. In an analogous way, such invisible beings (to us) as angels, jinn, and other spirit entities can become visible.
We read in Qur’an 19:17 that the spirit that Allah sent to Mary (the mother of `Isa [Jesus]), and whom Muslim scholars say is Angel Jibreel (Gabriel), appeared before her as a man. When Jibreel came to Prophet Muhammad (peace and blessings be upon him), he sometimes came as a man, in the shape of a Companion named Dihyah. For example, he came following the end of the Battle of the Trench and told the Prophet (peace and blessings be upon him), “O Messenger of Allah, you have taken off your armor but we, the angels, have not yet done so. Allah orders you to march upon the Banu Quraizhah.” (Bukhari and Muslim) Once Jibreel came as a man dressed in white and, in order to instruct the Companions in religion, asked the Prophet such questions as, What is belief? What is Islam? What is ihsan (excellence or perfection of virtue)? When is the Day of Judgment? (Muslim)
Like angels and jinn, Satan (who is a jinn) can appear in different forms. It is narrated that before the Battle of Badr, he appeared to the Quraishi leaders as an old man from Najd and advised them. Likewise, a Companion guarding Ramadan’s Zakah caught a disguised Satan trying to steal some items. Satan entreated the Companion to release him, which he did twice. On the third time, the Companion tried to take him to Allah’s Messenger. But Satan appealed, “Release me, and I’ll tell you how you can secure yourself against me.” The Companion asked what that was, and Satan replied that it was Ayat Al-Kursi (Al-Baqarah 2:255). When informed of this, Allah’s Messenger (peace and blessings be upon him) commented, “That one is a liar, but (on that occasion) he told the truth.” (Bukhari)
The Qur’an relates that a group of jinn listened to Allah’s Messenger recite the Qur’an and, when they returned to their people, said, [O people! Surely we listened to a Book that has been revealed after Moses, affirms what precedes it, and guides to right and the Straight Path] (Al-Ahqaf 46:30). The surah continues with what they thought about what they had heard. Some traditions tell us that the Messenger (peace and blessings be upon him) recited parts of the Qur’an and preached his message to the jinn.