Answer:
How one acts makes one beautiful or not, not his/her superficial looks. In other words, true beauty is not found in superficial appearance (his/her face and/or body is beautiful), but how one behaves and carries oneself defines the beauty in a person (he/she is a beautiful person). Beauty is as beauty does!
This common southern (U.S.) expression was morphed into "stupid is as stupid does" in the movie Forrest Gump, and as a result "stupid is as stupid does"is now more widely known than the original "beauty is as beauty does".