Angels are humanoid beings with large wings on their backs.
Often worshiped as divine beings, angels are manifestations of predominantly white mana , though some have been corrupted with black mana , and angels from Bant, Innistrad, and Ravnica have boasted traits from each of the other colors. Almost all known angels are female, intentionally so. The first creature to bear the type was Serra Angel from Alpha. Angel is the iconic creature for the color white.
Types of Angels
Copper-Leaf Angels were artificial angels created by Latulla to aid in the Keldon war effort against Jamuraa. However, they did not play a significant role in the Keldon invasion and likely fell into disuse following their creator's downfall.
Duler Angels were created by the Sages of Lat-Nam and were inspired by legends about Serra angels. The sage who created them based them on humans, giving them wings. Their purpose was to guard School of Lat-Nam and its secrets.
Fallen Angels were Serra angels, crowned with a Horned Halo, who were under the command of an Angel Keeper. Fallen angels tended to require sacrifices to remain strong. These were very powerful creatures, used by wizards as a means to gain more power. According to a Dominarian fable, an angel who dies as a fallen angel dies forever.
Angels of Vengeance
Angels who were summoned and bound to carry out acts against their nature lost their celestial nature and became material beings. Unlike other angels, they have dull feathers and highly predatory features. This process takes some time to happen, but with each act they fall further from what they once were.
Within the Boros, angels are considered to be incarnations of the spirit of justice and revenge. They are considered to be the top members of the guild, whose parun Razia is an angel herself. Razia created all other Boros angels as clones, reflections or copies of herself. They all lived in the floating hall called the Parhelion.
Boros angels possess no need to drink, eat, or sleep, but can if it so pleases them. They have enhanced strength, a strong sense of duty and morality, and are supposedly incapable of lying. Boros angels can hear people calling their name from anywhere in Ravnica.
Angels of Despair
The exact origin of the Orzhov Syndicate's angels is still unknown. They may be related to the Boros angels or were made as a copy of them, but either way they possess the same sense of duty. Orzhov angels are empty voids whose only fulfillment comes from performance of duty. They appear only on special occasions such as high ceremonies, where they inspire awe and fear in onlookers.
There are two types of Serra Angels. First, and one of the oldest forms of angels, are those associated with goddess Serra, who is probably worshiped on many planes. They are souls of brave warriors who rise in the form of angels, divine creatures of pure mana (though they can also conjure bodies). Even if defeated in battle, they can't be truly killed, and their souls rise again. Interestingly, goblins have used Serra Angel skulls to make their war drums (see Goblin War Drums). These angels played an important role in the rebellion of Epityr against Sheoltun. 
Serra, a planeswalker named after the goddess, created her own artificial plane, Serra's Realm, where she brought her own angels into being to populate her world. Their society was peaceful and harmonious until the arrival of Urza Planeswalker and the Phyrexians, the latter of whom brought with them black mana that corrupted the realm, drove away Serra, and led to Radiant's coup. The Phyrexian attacks against Serra's Realm also accelerated the plane's collapse, but Urza was able to evacuate some of the angels to Dominaria, where many still exist.
In the Shard of Alara called Bant, there are angels who are thought to be ultimate representations of its society's ideals. It is commonly believed that a noble life and death will lead a person to be reborn as one.
The most revered angel in Bant history was named Asha. History tells that she sacrificed herself to defeat the half-demon/half-dragon abomination Malfegor (though in reality, she simply banished him to the Shard of Grixis). Though she has been gone for many years, she left a powerful sigil that, until the Conflux, maintained safety and peace among her people. The faithful still pray to Asha, and some believe that she still might some day return.
Angels lend guidance to mortals, but otherwise they do not directly interfere with their lives. Among angels, there is a hierarchy with four different ranks.
The Asura are the highest ranked angels. There are only seven of them, which make up the Court of Orderly Contemplation. Only one has been revealed via the cards, Jenara who is the Asura of War.
The Amesha represent ideals, such as honor or justice.
The Mahra carry out the orders of the Asura and the Amesha.
Celebrants, as the lowest ranking angels, are responsible for protecting the lives and ideals of mortals.
The Flight of Goldnight
These angels are associated with the sun, in contrast with Avacyn herself. Once a year during the Harvest Moon season, the sun will not dip below the horizon for two full days, and during this time the moon isn't visible. Known as the Feast of Goldnight, this is the holiest day for the humans. It is the time when the Avacynian enchantments are strongest throughout Innistrad. Angels from this flight are the most battle oriented among the flights. They also oversee the training of cathars.
The messenger for Flight Goldnight is Gisela.
The Flight of Alabaster
These angels personify the Blessed Sleep and are associated with the Hunter's Moon season. They provide magic that wards against the desecration of dead humans. In the absence of Avacyn they remained the most active and continued on to reinforce wards that protected the human populations.
The messenger for Flight Alabaster is Bruna.
The Flight of Herons
These are the angels of birth and purity and are associated with the New Moon season. Their magic is said to ward humans against harm in life (as opposed to the Alabaster host, which wards against harm in death). Most of the angels from this flight helped in the efforts of humans against the werewolves.
The messenger for Flight Herons is Sigarda.
The angels were among the first creatures that attempted to mount a resistance against the original arrival of the Eldrazi but were easily defeated. Because of this, their halo is worn down over her eyes, symbolizing their blindness to the Eldrazi's atrocities and their powerlessness to aid her world. Over time the angels' forced aloofness was incorporated into the world's religions. The "deity" Emeria, for example, was conceptualized as a great angelic being, an impartial refuge in a dangerous world—her halo a sign of hope, not of separation. When the Eldrazi were released again, the halos of oppression shattered and the angels were given the opportunity to redeem themselves. 
- Akroma, Angel of Wrath
- Baneslayer Angel
- Bruna, Light of Alabaster
- Gabriel Angelfire
- Gisela, Blade of Goldnight
- Iona, Shield of Emeria
- Linvala, Keeper of Silence
- Radiant, Archangel
- Razia, Boros Archangel
- Reya Dawnbringer
- Sigarda, Host of Herons
- Angelic Accord
- Angelic Favor
- Decree of Justice
- Devout Invocation
- Entreat the Angels
- Geist of Saint Traft
- Luminarch Ascension
- Moonsilver Spear
- Sigil of the Empty Throne
- Urbis Protector
- Doug Beyer. (December 17, 2008.) "Insights from the Inbox", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Magic Arcana. (June 24, 2004.) "Black's Tall Angels", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Mark Rosewater. (August 01, 2014.) "The fact that all angels are female has come up a few times here. I noticed that all demons happen to be male. Is that intentional too?", Blogatog, Tumblr.
- Mark Rosewater. (March 20, 2012.) "Marquee creatures for the colors", Blogatog, Tumblr.
- Aaron Forsythe. (June 25, 2004.) "Angels in the Outfield", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Magic Arcana. (February 26, 2004.) "Tall Angels", Daily MTG, magicthegathering.com, Wizards of the Coast.
- The Colors of Magic
- Mark Rosewater. (June 21, 2004.) "Que Serra, Serra", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Monty Ashley. (October 21, 2010.) "From the Library of Leng: Serra Angel", Daily MTG, magicthegathering.com, Wizards of the Coast.
- Doug Beyer. (April 14, 2010.) "The Defiance of Angels", Daily MTG, magicthegathering.com, Wizards of the Coast.