All that glitters is not gold

 All that glitters is not gold,

Many a times you have been told. 

Many men, his life he sold, 

to outside appearances behold,

gilded tombs do worms enfold. 

If you had been as wise as your were bold,

young in limbs and in judgement old, 

your answer would not have been as inscrolled.

https://nosweatshakespeare.com/quotes/famous/all-that-glitters-is-not-gold/

This full ‘All that glitters is not gold’ quote requires some context and an explanation.

The beautiful, educated and highly accomplished young Portia has been left with a fortune on the death of her wealthy father. Concerned, before his death, that his daughter would be vulnerable to fortune hunters he stipulated in his will that all suitors would be subjected to a test. They would have to correctly pick one of three caskets that contains Portia’s picture, to claim her hand in marriage. One of the caskets is made of gold, one silver, and the last one is made of base lead.

Suitors line up to undergo the test. The first suitor (the Prince of Morocco) chooses the gold casket and opens it to find a skull with a rejection letter including this ‘all the glistens’ quote. His preference for gold has proved to be deceptive, and Portia’s comment as he leaves is ‘a gentle riddance’.

The second suitor chooses the silver casket and finds a puppet of a jester.

A poor young Venetian, who is poor and has to borrow money comes to Belmont to woo Portia. He chooses the lead casket and reveals her picture within. She returns to Venice with him to marry.

In ‘all that glitters is not gold,’ Shakespeare finds a perfect, beautiful image to express a profound truth, and as such has become one of his most recognized quotes. In this case, that love is not a matter of a superficial shiny object but is full of some more dreary things like responsibility and obligation.