In an analogous way, such invisible beings as angels, jinn, and other spirit entities are clothed in some material substance, such as air or ether, and then become visible. According to Imam Shibli, God may allow them to assume a form when they utter any of His Names, for this functions like a key or a visa enabling them to assume a form and become visible in this world. If they try to do so without God's permission, by relying on their own abilities, they are torn into pieces and perish.
We read in Qur'an 19:17 that the spirit God sent to Mary (the mother of Jesus), and whom Muslim scholars say is Archangel Gabriel, appeared before her as a man. When Gabriel came to Prophet Muhammad, upon him be peace and blessings, with Revelation or God's Messages, he usually came as a warrior, a traveler, or a Companion named Dihya. For example, he came as a warrior on horseback following the end of the Battle of the Trench and told the Prophet, upon him be peace: "O Messenger of God, you have taken off your armor but we, the angels, have not yet done so. God orders you to march upon the Banu Qurayza." Once he came as a traveler 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?
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 Qurayshi leaders as an old man from Najd and advised them. Likewise, a Companion guarding the spoils of war 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 God'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 the Verse of the Throne (2:255). When informed of this, God's Messenger, upon him be peace and blessings, commented: "That wicked one is a liar, but on that occasion he told the truth." 
The Qur'an relates that a group of jinn listened to God'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" (46:30). The sura continues with what they thought about what they had heard. Some Traditions tell us that the Messenger, upon him be peace and blessings, recited parts of the Qur'an and preached his Message to the jinn.
Jinn can also appear as snakes, scorpions, cattle, donkeys, birds, and other animals. When our Prophet, upon him be peace and blessings, accepted the jinn's oath of allegiance in the valley of Batn al-Nakhla, he wanted them to appear to his community either in their own form or in other agreeable forms, not as such harmful animals as dogs and scorpions. He warned his community: "When you see any vermin in your house, tell it three times: 'For God's sake, leave this place' for it may be a friendly jinn. If it does not leave, it is not a jinn. If it is harmful, you may kill it."
The jinn who gave allegiance to God's Messenger promised him: "If your community recites the basmala (In the Name of God, the All-Merciful, the All-Compassionate) before anything they do and cover their dishes, we will not touch their food or their drink." Another Tradition says: [When you have relieved yourselves] do not clean yourselves with bones and dried pieces of dung, for they are among the foods of your jinn brothers.