It is a very rude and offensive expression and should not be used in polite conversation.
Here's why:
* Insulting: It is a direct and aggressive command, implying that the speaker considers the listener to be annoying or undeserving of their attention.
* Vulgar: "Gueule" is a vulgar term for "mouth" and carries a connotation of rudeness and disrespect.
* Aggressive: The phrase is often used in anger or frustration, adding to its offensive nature.
In most situations, it is best to avoid using "ferme ta gueule" altogether. There are many more respectful and appropriate ways to express yourself in French.
If you are trying to learn French, it's important to be aware of the cultural nuances of language and avoid using expressions that could be considered offensive.