Plot defines what happens.
Story explains why it happens.
Theme explains why it’s important.
Think of a story that’s nothing but plot. That creates a lot of action and excitement, but ultimately it makes little sense. Bad karate movies and action thrillers are often nothing but plot like bad James Bond movies (“A View to a Kill”). In stories that contains nothing but plot, you get a lot of action but you don’t know why anything is happening other than people running around to avoid getting hurt or killed.
Plot alone is never enough to create a great movie. You also need a story. A story explains why things happen and that can only come from the motivation behind your hero and villain. When your hero and villain are motivated to take action to achieve a goal, then they’ll do something and that creates action. Now the action doesn’t exist just for the sake of more and bigger action, but because either the hero or villain are trying to accomplish a goal.
Watch the original “Die Hard” film and then watch the progressively bad sequels that strip away the story behind the hero and villain and focus mostly on action or plot. We don’t want to know what happens. We also want to know why things happen.
It’s easy to create a plot-driven movie. Show the hero walking down the street and a zombie jumps out. Now the hero runs away to the stop of a house. Then have a UFO suddenly appear in the sky and shoot lasers at the hero. Now the hero jumps down and runs away from the zombie and the UFO. Suddenly a bunch of soldiers start shooting a machine gun at the hero. Lots of action, lots of explosions, lots of gunfire, and lots of action, but there’s no meaning behind it other than the hero running for his life.
Now if you add a story that explains why something is happening, you have a better tale to tell. The forces opposing the hero don’t use appear out of nowhere for no reason but because the villain is trying to achieve a goal of some kind. In “Die Hard,” the villain doesn’t just send an army of terrorists after the hero just for action but because the villain wants to fulfill and complete a plan to steal corporate bonds and escape.
Plot and story are often where most movies stop, so you need to go one step further and add a theme. A theme explains why the story is important. “Terminator 3” is nothing but action. “Terminator 2” is plot, action, and a theme that explains the importance of human life. That’s the whole purpose of “Terminator 2” so it makes it a far superior film compared to “Terminator 3”.
When turning your idea into a screenplay, focus on plot, story, and theme. With all three elements, you’re far more likely to create a great movie than just relying on plot or plot and story alone.