Metrophanes was Bishop of Smyrna (now Izmir, Turkey) near the end of the 9th Century.
He was a partisan of Rome in her contest with Photius, and adherent of his rival, Ignatius.
His chief hymnological works were his Canons in honor of the Trinity, eight in all, one for each Tone.
If you know where to get a good picture of Metrophanes (head & shoulders, at least 200×300 pixels),