All that glitters/glistens is not gold
Definition 1 of 1
Pro Tip 1/3Metaphorical Meaning
The phrase implies that outward appearances can be misleading, suggesting caution in judgment. 
The shiny car seemed perfect, yet it broke down in a week -- all that glitters is not gold.
Pro Tip 2/3Cultural Context
This phrase comes from old wisdom, used in literature and speeches to teach about cautious optimism. 
In his novel, the character learns that all that glistens is not gold, as fortune often comes with hidden troubles.
Pro Tip 3/3Emotional Connotation
It's often used to express disappointment when something is not as good as it initially seemed. 
She was upset about the cheap jewelry that tarnished: all that glitters is not gold.