How can one construct an "urban/rural" variable from the ACS "Metro" item? Are unidentifiable records metro?

Decennial censuses provided an “urban/rural” indicator which utilized the concept of an “urbanized area”. I wish to empoly a similar concept using the 2010-2014 ACS data but am unable to find any item but “metro” that addresses this charactistic. Is “metropolitan/non-metropolitan” a reasonable substitute for "urban/rural? Why does the ACS not include an "urban/rural"variable?

IPUMS-USA has the variable URBAN that acts as an indicator of whether a household’s location was urban or rural. This variable, however, is very problematic due to the constantly changing definitions of “urban” and “rural”. The variable description for the URBAN variable has a nice history of the Census Bureau’s use of the rural/urban distinction through the years. Ultimately, it is very difficult for a rural/urban variable to carry any meaning or comparability over samples that span multiple years. The METRO variable may be of best use for your purposes, although you should be aware of the confidentiality and sampling issues associated with the METRO variable, available on the comparability tab.