Mules are known for their strong will and resistance to being controlled. They are often described as being stubborn, headstrong, and difficult to persuade.
So, when someone is described as "as stubborn as a mule," it implies they are:
* Resistant to change: They refuse to budge from their position, even when presented with evidence or reason to do so.
* Uncompromising: They are unwilling to negotiate or compromise, even if it would be beneficial to do so.
* Fixed in their ways: They stick to their beliefs and routines, even when they are outdated or impractical.
This simile can be used in a humorous or critical context, depending on the situation.