In DMC, actual details about angels are pretty much entirely nonexistant. We know that they exist and that some kind of higher power exists, thanks to the Goddess Statues and the Holy Water, but beyond that, the series doesn't really give us anything.

As such, Kane -- and the combat-angels of heaven (rather than the human souls that ascend) -- operate under these points.

1) They, like demons, can take a human form if they so please. Their human form is somewhat modifable in terms of age, but otherwise set (IE, their colors, their appearant nationality, etc.)

2) They also have their own version of the Devil Trigger (which Kane just shrugged and named "Angel Trigger") that allows them to turn into a more powerful, if still humanoid, form. These forms give off an immensely choking, intimidating aura, even if the angel themselves has no intent to harm or oppress -- it's simply a side effect of it. The actual appearance can range from mostly humanoid but armored, similar to the canon Devil Triggers, to something with eyes and mouths where eyes and mouths should really not be. (Both of these facts tends to be why angels picked up "Be not afraid" as their catch phrase)

3) They cannot become an equal of Devil Arms. If an angel dies, its power disperses into the land itself to fuel and flourish it, meaning they leave none of the power behind. To put it simply, angels are "selfless" enough to fuel the world with their deaths, while demons tend towards being "selfish" and wanting to remain (thus the condsensing of their power instead of it dispersing).

4) However, an angel's body tends to be just as strong as a demon's, and parts of them can be used for various things; as an example, Kane often gathers the loose feathers he sheds because they can be used to purify and bless water, or -- as Lady is more interested in -- forged into holy-elemental bullets. Generally, only the angelic parts of an angel will work, so shards of "armor" shed from their Trigger or their feathers is the go-to.

5) As well, an angel has a third trick up their sleeve: their "feral form". While not used as often, an angel is "born" with a bestial form as tied to them as the human and Trigger forms are. These forms are often of fantastical animals, and it's theorized that just as the stories and rumors of Sparda came about because the man existed, the stories about things like unicorns and dragons came from when angels were once around. These forms tend to be stronger than their humanoid forms, but are much more unwieldy -- try fitting a dragon through a church doorway and it's clear why they don't use them as often.