All that glitters is not gold

Appearances can be deceiving; something that looks valuable or attractive may not actually be so.

This wisdom traces back to Aesop's fables and was popularized by Shakespeare in "The Merchant of Venice" (1596) as "All that glisters is not gold." The phrase evolved from earlier Latin versions and reflects humanity's ancient understanding that surface beauty can mask worthlessness, like fool's gold fooling prospectors.