[1] The nomen Metilius appears to belong to a class of gentilicia arising from diminutive versions of other names, originally ending in -ulus.
They were admitted to the senate, implying that they were originally patricians, but all of the Metilii mentioned during the time of the Republic were plebeians.
[1][3] The Metilii of the Republic do not appear to have been divided into branches, the only surname being Croto, an apparent reference to Crotona, an ancient Greek city in Bruttium, which played an important part in the Second Punic War.
Under the Empire, the leading family of the Metilii bore the surname of Nepos, literally "grandson".
Several consuls of the late first and second centuries were descended from this family, through both the paternal and maternal lines, and are included here if they bore the nomen Metilius, even though, strictly speaking, some of them belonged to other gentes, such as the Atilii.