That's the point, I think. Most metro areas are made up of a collection of many incorporated areas which collectively make up what people think of as the city. Some of those incorporated areas are large, some are small, and you might not realize you're driving from one to another since nothing changes except which legal entity collects the property taxes.

Yeah, my city totally surrounds several sub-50k "towns", plus has several others glommed on to the side of it that you'd be forgiven for not realizing are separate from the city, and it's not even an extreme case (see St. Louis for that)