How is a role considered leading vs supporting?

Question

Are there any rules or other metrics that help determine if a role is considered a leading one or a supporting role? Or is it more like a gut feeling? Clearly, the choice is obvious in many movies such as *Terminator* or *Pitch Black*. But how do they determine the lead when there are several "main" characters to choose from? \n\nFor example: *Lord of the Rings* had Elijah Wood (Frodo), Ian McKellen (Gandalf), and Viggo Mortensen (Aragorn). Or *Pulp Fiction*'s John Travolta (Vincent), Samuel L. Jackson (Jules) & Bruce Willis (Butch). How did they determine who was the leading role?\n\n(Not sure what tags to put on this one)

Answer 1

LEADING ROLE is a character/actor that is most of the feature film. The lead character(s) is the reason the other characters are needed. They lead the story. The lead is the "protagonist". The lead has the largest part in the project.

SUPPORTING ROLE is exactly that! Supporting the lead actor. The supporting role gives a connection from one scene to another or connection from one character to another. Supporting actors have more lines that a "day player"/bit part and usually have a meaningful connection with the LEAD ROLE.