Metru were districts in the city of Metru Nui. There were six Metru: Ta-Metru, Po-Metru, Onu-Metru, Le-Metru, Ko-Metru, and Ga-Metru.
Each Metru was named for the element it most represented. The prefix was Matoran for that element.
"For Toa used to the crowds and tall buildings of their metrus, this place was unsettling."