Well, finally I found a source that mentions metallic like beings. The author is also a channel. Her name is Barbara Hand Clow and the book's name is "Pleiadian Cosmology".
You can read it in whole at http://www.scribd.com/doc/38961952/Barbara-Hand-Clow-Pleiadian-Cosmology. On page 69 there is a part where the difference between Lizards and Niburians is being discussed:
"The Nibiruans differ from us by having a metal biology. From your perspective metallic life forms are non-biological. To understand the lifestyle Nibiruan you must be able to expand your imagination and include a metallic force your vision of what which is biological."
So perhaps my mini mystery about the unknown being that I mention in one of my previous articles is solved...for now :)
