Mettius
Person
Gallic War 1.47 supplies the first indexed source portrait: “… It seemed [therefore] most proper to send to him C. Valerius Procillus, the son of C. Valerius Caburus, a young man of the highest courage and accomplishments (whose father had been presented with the freedom of the city by C. Valerius Flaccus), both on account of his fidelity and on account of his knowledge of the Gallic language, which Ariovistus, by long …”
Named form in selected editions; identity established only to the extent of the cited context.
Gallic War 1.47
Caesar
… It seemed [therefore] most proper to send to him C. Valerius Procillus, the son of C. Valerius Caburus, a young man of the highest courage and accomplishments (whose father had been presented with the freedom of the city by C. Valerius Flaccus), both on account of his fidelity and on account of his knowledge of the Gallic language, which Ariovistus, by long practice, now spoke fluently; and because in his case the Germans would have no motive for committing violence; and [as his colleague] M. Mettius, who had shared the hospitality of Ariovistus. …
Gallic War 1.53
Caesar
… M. Mettius, also, was found and brought back to him [Caesar.]