The Metron Consortium was the political state for the Metrons. (ST reference: Star Trek Star Charts)
The Federation's first contact with the Metrons was made in 2267 by Starfleet Captain James T. Kirk of the USS Enterprise. (TOS episode: "Arena")
By 2373, the Metron species was dying out. They lured Captain Benjamin Sisko of the USS Defiant to their space with a false distress call so he could help preserve their knowledge for future generations. (DS9 short story: "Where I Fell Before My Enemy")
Also in 2373, the Metron Consortium signed an agreement with the Verillians. (DS9 episode: "Business as Usual")
Two years later, in 2375, then-Governor Nanietta Bacco of Cestus III negotiated an historic peace treaty between the Federation and the Metrons following an attack on the world by the Gorn Hegemony.
In an alternate timeline, the Metron Consortium fought the Battle of Cestus against the Klingon Empire. (ST - Myriad Universes novel: The Tears of Eridanus)