He first appears in George Pachymeres' History in the year 1273 as one of a small group of clerics who backed the Emperor Michael VIII Palaiologos's negotiations for ecclesial union with Rome.
Following the Council of Lyons, he served for a time as Michael's ambassador at the papal courts of Gregory X, Innocent V, John XXI, and Nicholas III; among other things, he argued, unsuccessfully, for a joint Greek-Latin crusade against the Turks.
After the Union of Lyons was dissolved following the Emperor Michael's death (December 1282), Metochites, along with the patriarch John Bekkos and the archdeacon Constantine Meliteniotes, found himself in political disfavor; anti-unionist councils at Constantinople in 1283 and 1285 reduced him to lay status and charged him with heresy; and he spent some 45 years — by far the greater portion of his life — in prison for remaining loyal to his unionist beliefs.
His son, Theodore Metochites, who did not share his father's views on union with Rome, gained great wealth and influence under the Emperor Andronikos II, and was a renowned Byzantine humanist; among his pupils was Nikephoros Gregoras, the historian and anti-palamite theologian.
[his writing is] altogether difficult, harsh in composition, softened by no false dye or meretricious adornment, with sober, somber opinions, and solid arguments for proving what he has in mind, but terrible and crabbed in his elocution and choice of words."