Magick cannot and will not allow you to become anything but human. Magick works within the laws of nature, altering the inner world and interacting with it, as well as subtly altering the strings of fate.
That said, the previous points are spot on in relation to what fairies actually are. They aren't cute little flower sprites that do good things and grant wishes.
To quote one of my favorite films...
Sarah: Ow! It bit me!
Hoggle: What'd you expect fairies to do?
Sarah: I thought they did nice things, like... like granting wishes.
Hoggle: Shows what you know, don't it?
Fairies are chthonic spirits that dwell in the underworld, Elphame, and are dangerous in folklore. They can abduct people, cause blights on livestock and crops, disease, feed on their souls, steal infants, and other debachery.
They can range from beings not far off from the fallen angels of the Book of Enoch, the luminous beings, to the spirits of the dead, to wights of the land itself. Some are even gods. Even the black devil of European folklore was considered a fairy lord.
I personally consider them the same thing as demons and jinn (jinn are essentially the fairies of the middle-east, rooted in ancestor and spirit worship), synonymous with the term spirit.
Now one can certainly work with the goode folk. But they aren't nice & sweet things. Some are even "evil", like the Sluegh, a Scottish fairy that is essentially a swarm of unbaptised spirits that smell like rotting flesh and grab people to drop them off great heights. Fun times eh?