Yes they do exist, and in many kinds. It is my opinion that usually if you are seeking first and foremost the thrill of meeting one (or if you are just blindly reliant upon and worshipful of technology, power tools, and power images in general), then you may end up in some kind of ego situation with lower beings, like those "Greys" who have not been at all nice to their abductee victims, leaving them quite confused as to what was astral, physical, or provoked imagination. The problem might be comparable to hanging around bars late at night just to check out the motorcycles, sports cars, big guys and babes - you can get into some nasty misunderstandings with some really bad characters for such behavior. I find this to be the frightening case for much of our culture today, which is playing with fire as it markets to children the images of aliens and monsters without taking them seriously for what they can be unlocking our volitions to.
If however you are willing to take the matter of extraterrestrials seriously enough without being fixated, and you're simply open to meeting ships of light and unearthly friends of all shapes and sizes in the courses of your missions of love, (whereupon you are prayerful, respectful, and willing to be guided and protected by God and your conception of God's divine helpers), then you will have nothing but good experiences with the countless beings outside of the human forms, beings who will generally touch your life only gently and astrally so as to not be too intrusive upon your Earthly pattern. I've been on some super spaceship rides astrally with some really nice beings - the rides ended when I got crude in my thinking, not they. I suspect that it is usually the humans who are stumbling about the astral realms who are invading the extraterrestrials, and not the other way around.
So given that we can take responsibility both as individuals and as a species for the quality of our extraterrestrial contacts going into the future, I do want to make clear my sympathies for those who have truly suffered in the past. Their's is not my area of expertise, but I'm a believer and just maybe a sufferer as well. There is a point in space-time to which I find myself sometimes returning in lucid dreams and out-of-body, where as a child I was convinced of a traumatic paralysis and alien visitation against my will; it is still submerged in my mind, triggered by chance circumstances, much as the abductees claim. Pending a better understanding, I can only suggest that we all be more empathetically aware of how much our spiritually-denying and technologically-glorifying society, misguided as it has been and may be yet for a while, has encouraged bad contact experiences for lack of validating anything better. Aliens and angels may have been considered equally crazy when we were growing up, but at least emotionally we could find more belonging by injury than by illumination.
Humans are spiritual beings, and we will hunger and thirst for relationships that are out of this world; they will nourish us, even when they are abusing. So if you are feeling ambivalence and injury at the hands of something metaphysical, be it demonic, alien, black magic, or other, be brave enough to celebrate your spiritual nature as distinct from the callousness of that bad experience, and dare to call for a higher and kinder contact for the next time. Contrary to what you may have been told (by those who might be celebrating their own injuries as some badges of courage), it is negativity which is distant, meaningless, and fickle, and positivity which is all the more close, intimate, persistant, indicative, and available the higher you go, from good spirit friends and other dimensional beings, all the way up through your own spirit guides, your higher self, and the God and the Goddess and the Great Spirit of All. The ones who know how to love you are the ones who have the power and the willingness to come when you call, to know where you are and to share your life always. You were made to meet love, even if you have already discovered your yearning for this to be true in a sad lack of the experience.