Metonymies often rely on cultural knowledge, like using 'the pen' for writers or 'the press' for journalism. In debates, 'the pen' is mightier than 'the sword.
Pro Tip 2/3
Not Literal
Metonymy isn't literal; it uses one concept to stand for another related concept. The 'suit' walked into the room, meaning a businessperson.
Pro Tip 3/3
Parts for Whole
Sometimes just a part of something is used to represent the whole, like 'wheels' for car. Nice 'wheels'—did you just get the car?