In a bad movie, things seem to happen for no apparent reason. When the reason behind the plot doesn’t make sense, then the story is much weaker as a result. That’s why the motivation behind your main characters must be clear, strong, and emotional so we know exactly why they’re doing what they’re doing.
For an example of poor motivation, watch “Mortal Engines,” which is about a time in the future where cities like London are on wheels and race around the planet, gobbling up smaller towns to consume their resources.
While this odd premise is fine, the motivation behind the main character makes no sense. [SPOILER ALERT] Apparently the hero is a young girl who wants to kill the leader of London because he killed her mother. Yet the reason why he killed her mother is vague and abstract.
Apparently the hero’s mother found an artifact that the leader of London recognized as important for creating a doomsday-like weapon. How this artifact is so important isn’t shown so it’s like someone holding up a rotten pineapple, claiming it’s important, and then killing everyone around them to possess it.
Because we don’t understand how this artifact is so important, seeing the villain kill the hero’s mother weakens the hero’s motivation against the villain.
Even stranger, the hero grew up with her mother and the villain and after living with her mother and the villain for much of her childhood, she finally learns at the end that the villain is actually her father.
How did the hero ever conclude that the man who raised her during her childhood was not her father and why is she surprised that he is? “Mortal Engines” is a perfect example of weak and muddled motivation.
Now look at the motivation in “The Little Mermaid.” Ariel yearns to visit the human world so she collects human artifacts. When she angers her father, Neptune, he destroys her treasured artifacts that we’ve seen her delight in playing with them.
Watching Neptune destroy her collection of human artifacts provides clear motivation for why Ariel would make a deal with the Sea Witch to become human.
Not only is Ariel’s motivation clear, but it was set up earlier by showing us Ariel’s love of human artifacts. Watching Neptune destroy Ariel’s collection provides a massive emotional kick in the pants for her to take action and become human by seeing the Sea Witch.
That’s a clear, understandable motivation that’s far more logical and powerful than the weak motivation for the hero in “Mortal Engines.”
In your own screenplay, make sure all characters have a logical and emotional reason for taking action. Elle in “Legally Blonde” went to law school to chase after her boyfriend who broke her heart because she thought he was going to propose to her but broke up with her instead.
Katniss in “The Hunger Games” had a clear reason to volunteer for the Hunger Games to protect her little sister. We saw Katniss trying to calm her little sister in the beginning so it’s logical that she would take action and take her little sister’s place. With the consequences being life and death, Katniss’s action is clear, logical, and highly emotional.
So make your characters’ motivation clear, logical, and emotional, and the rest of your story will have a solid foundation to rest upon.