Among the many accolades that critics bestow on Catullus, one is often absent: metrical revolutionary. This is strange, for we know of no other Roman poet who combined so many poetic forms across so many genres for so many purposes. In what, by other standards, was a brief poetic career – perhaps not even a decade long – we find no fewer than fourteen different metrical forms, two of which may well have been his own innovation. And far from this being an incoherent medley of disparate metres for variety’s sake, it emerges as a coherent and inventive collection curated by a masterful hand. The purpose of this chapter is to survey the range of Catullus’ deployment of metrical forms and to demonstrate the nuanced flair of his practice.