all that glitters is not gold

The phrase "all that glitters is not gold" is an idiomatic expression that means things that appear attractive, promising, or valuable at first glance may not always be so. It warns against judging something solely based on its outward appearance or initial impression, as it may be deceptive or false. This phrase reminds us to look beyond superficiality and consider the true nature, substance, or worth of things before making judgments or decisions.