Etymologically, the word comes from the Greek metoikos, from meta, "change," and oikos, "house."
The Greeks differentiated foreigners in the city who were Greek from those who were not Greek (metics). Free foreigners who came from Greece, but who were born to metic parents, were also considered metics. Resident Greek foreigners were considered free men, while non-Greek foreigners and barbarians were suspect, as one could never be certain that a foreigner was really a free man (eleutheros). The city, therefore, had to be cautious and watch them, as long as this did not interfere with hospitality or asylum, which the Greeks valued highly. However, the expulsion of foreigners (xenelasia) was a common practise.
Although they were residents, barbarian foreigners had no special legal protection. Greek foreigners had no political rights but had certain fiscal obligations. Marriage between a metic and a citizen woman was not recognized. Metics were reigstered, like citizens, within a deme, but had to find a prostates (patron) who could vouch for him, and a proxenos who would represent him in court. Patrons would purchase land and hold it in behalf of the metics, who could not own their own land. Depending on the city, a metic might also have to contribute financially to the religious liturgies, and could have military obligations as a simple soldier. Metics were always put under certain controls, but the importance of the controls depended on the cosmopolitan character of the city and the possible bilateral legal conventions between cities.
Free Greek foreigners were excluded from politics, but they belonged to the same community as citizens, sharing a language, religion, and sanctuations. The right of citizenship was rarely granted, but the practise of hospitality (xenia) offered certain guarantees. Generally, cities did not aim to integrate foreigners as full citizens.
Metics often oversaw Hellenic commerce and banking and formed part of the governmental bureaucracy.