History
Metroliths are homeless silicon-based hive organisms. They're like sentient termite mounts. Phenomenally difficult to communicate with, but not hostile. When they saw the craved mountain Rushmore they belived that it was creature like them and were decapitated. The y started to attack every human they see, but when they find out the truth they were very embarrassed and offered to do anything to be forgiven. Tourist would come from all over the country to see them.