* Metropolis: A large city, especially the capital or chief city of a country or region.
* Metropolitan: Relating to a large city or its inhabitants.
* Metronome: A device that produces regular clicks or beats to help musicians keep time.
* Metro: A system of underground railway lines (often abbreviated from "Metropolitan").
* Metrology: The science of measurement.
* Metron: (Less common) A unit of length equal to about 1.09 yards.
These are just a few examples. There are other, less common words that start with "metro" depending on your field of study or interest.