A more thorough explanation:

A metropolitan district is a special district created by a state to provide unified administration of one or more common services, such as water supply or public transportation. It can include parts of or entire cities and towns in a metropolitan area.

For example, the Metropolitan Transportation Authority (MTA) in New York City is a metropolitan district that provides public transportation services to the entire metropolitan area. Another example is the Metropolitan Water District of Southern California, which provides water supply to the region.

These examples illustrate how a metropolitan district can provide essential services to a large and densely populated area, which may be difficult for individual cities or towns to manage on their own.