Why is "COUNTY" not the same as "METFIPS" for an individual in CPS?

Why is “COUNTY” not the same as “METFIPS” for an individual in CPS?

As I understand from variable description, both variables are fips code. I am looking at an individual in 2010 and both “COUNTY” and “METFIPS” are not masked.

It is correct that both COUNTY and METFIPS use FIPS coding schemes, however, they identify different levels of geographies. In IPUMS CPS COUNTY is a concatenation of the FIPS state code with the FIPS county code for identifiable records. On the other hand METFIPS identifies metropolitan areas (e.g. an areas surrounding and including cities).