Muslims believe that angels were created by God from pure light. Belief in their existence encompasses the Islamic faith itself. Belief in angels is one of the six Articles of Faith, without which there is no faith. The Qur’an states that these Articles are: "The Messenger believes in what was sent down to him from his Lord, and the believers: Each one believes in (1) God, (2) His angels, (3) His Books, (4) His Messengers, (5) the Last Day, and (6) that predestination, both good and evil, comes from God. " (Qur’an II:285). It is interesting to note that the Qur’an states that angels do not possess Free -Will, and therefore can only follow the instructions given by God. This is in contrast to Jinn who are not angelic, being made of smokeless fire. They do possess free-will so they can disobey or God.
Unlike in Christianity, there is no concept of a fallen angel in Islam as none can disobey God and therefore cannot fall from grace.

They were created for the sole purpose of serving God and being made from light, they can assume almost any form, which will appears real to the human eye. They belong to a level of existence beyond the perceptible world of phenomena, called `alam al-ghayb.

The root meaning of angel in Arabic is “messenger” which can be related to the Archangel Gabriel who revealed the Qur’an to the Prophet Mohammad.

The Qur’an refers to angels in a number of passages:

“Gardens of Eden which they shall enter ... and the angels shall enter unto them from every gate.” (13:23).

“The angel of death, who has been charged with you, will gather you; then to your Lord you will be returned.” (32:11).

"If you could only see when the evildoers are in the agonies of death and the angels are stretching out their hands: 'Give up your souls!' " (VI, 93). "Believers, guard yourselves and your families against a Fire whose fuel is men and stones, and over which are harsh, terrible angels" (66, 6).

“There are over you watchers, noble writers, who know whatever you do.” (82:10-12)
“Over every soul there is a watcher.” (86:4).

Unlike the Christian tradition, Islam has no firm hierarchical structure for angels, those mentioned in the Qur’an only seem to have specific rolls as an example Ridwan is the name of the angel who governs paradise. However there is a discenable structure as far as seniority is concerned. Those angels that appear to hold this seniority are:

Jibra'il (Jabriel, Jabril, Jibra'il, Jabriyel, Abru-El, Abruel), Gabriel, is the spirit of truth, who dictated the Quran to Mohammed . The angel who communicates with the Prophets. In appearance he has twelve wings and on observing his actual appearance the Prophet Mohamed fainted at his sight,
Mikail (or Mikaaiyl or Michael). Archangel of sustenance and the rewarder of good deed performed in this life. He stands above the seventh heaven.

Israfil (or Israafiyl or Raphael).The Angel responsible for announcing Judgment Day, by blowing on his horn ( In the Christian Tradition this is the duty of the Archangel gabriel). It is said that he has four wings two of his wings fill each of the compass quarters, East and West, the next covers his descent from heaven and the last wing he used to make himself invisible.

Izra'il (or Azrael). Izra'il is the Angel of Death who is responsible for releasing the soul from the physical body of man. It is also indicated that this angel will appear as a terrifying demon to those souls who have lead evil lives on earth, whereas the souls of the good shall see a beautiful angelic form.

Mikail (or Mikaaiyl or Michael). The angel of sustenance. He can also be liked to the angel of karma as he is responsible for rewarding those who have lead good lives.

The other angels mentioned in the Qur’an are:

• Malik is the angel who governs Hell and Hell Fire.
• Ridwan is the angel who governs Paradise.
• Kiraamun kaatibeen the two angels that sit on mankind’s shoulder and records good and bad deeds performed by that person.
• Munkar and Nakir the angels who interrogate a person in the grave about his good and bad deeds.
• Harut and Marut are the angels who were given the attributes of Man (Free-Will_ and when sent to Earth by God committed the sins of Man.

The angels therefore record the deeds of each individual from birth to death. They are your constant companion and assist those who seek the path to spiritual enlightenment.