Po-Metru, along with the other regions of Metru Nui, was created with the island. It became one of the most industrial locations on the island.
Being mostly barren, Po-Metru had little to offer industrially until the natural Carving abilities of its inhabiting Po-Matoran became known. The industry was largely based around sculpting and construction.
This attracted the attention of other Matoran and the conflict escalated when Onu-Metru sided with Ta-Metru while Le-Metru allied with Po-Metru. It has been said that the Ko-Matoran tried to stop the conflict but then ended up siding with Po-Metru and Le-Metru. The Ga-Matoran tried to remain out of the conflict but was eventually dragged onto Ta-Metru and Onu-Metru's side.
The actions of the two sides did not become militant for a long time but war eventually broke out between the cities. Work was abandoned by most Matoran and fighting started in the streets. The Turaga, who served as the island's leader at the time, did little to prevent the conflict, which was possibly why he was replaced by Turaga Dume.
Eventually, as Metru-Nui's trade stopped and started causing problems elsewhere in the Matoran Universe, Makuta Miserix assigned Makuta Teridax to stop the war. Teridax did this by gathering a large number of rebels and had them sealed in the Archives. He then unleashed the Rahi on them. This ended the war abbruptly but created a poor relationship between the Matoran of Metru-Nui and the Makuta.
Toa/Dark Hunter War
Po-Metru also served as the final battleground in the Toa/Dark Hunter War. After Toa Mangai Nidhiki helped to lead an army of Toa into a Canyon in Po-Metru then betrayed them as they were ambushed by Dark Hunters.
However, Toa Lhikan had anticipated this betrayal and had organized a second army of Toa to arrive and ambush the Dark Hunter, who then surrended and left the island, ending the war.
The Matoran of Po-Metru later resided in peace for a time until the Morbuzakh became known as a threat to all Matoran of Metru-Nui. Due to the plant's love of warm environments it would nest in the Cabled Vats that were transported across Ta-Metru. The Morbuzakh still managed to do significant damage to Po-Metru and was responsible for the disappearances of several Po-Matoran. Luckily, the Toa Metru were able to destroy the King Root and free the island.