What is the purpose of metonymy?
It's a word used to stand for other word..and it's sometimes chosen because it is a all known characteristic of that word..
A pen is mightier than sword..here pen is for written word and sword for millitary
See we use crown in place of royal person
We use white house for president..
The suits in place of business people
Dish for entire plate of food..
We use eyes for sight..
Now carefully analyze the capitalised sentences...
We must wait to hear from the CROWN until we make any further decisions..
The WHITE HOUSE will announce decision at noon..
The CUP is quite tasty..
Learn to use your EYES properly..
I hope this explanation is beat