I've recently re-read a great book called 'Alien Intrusion: UFOs and the Evolution Connection' by Gary Bates. Gary is a Christian/creationist who has studied the subject for years and his book is well documented and referenced.
Among his observations are:
The messages from 'aliens' seek to re-interpret the Bible. Never the Bhaghavad Gita, nor the Koran, but always the Bible. This gives us a clue as to who is behind these visitations.
Throughout history, these appearances has taken the forms familiar to the cultures to which they appeared (canoes, shields, etc).

There is too much information in this book to go into great detail; all I can say is that I highly recommend it. It is available from Creation Ministries International.

Hope this helps.

Yours in Him