Anybody who has read a book and watched its movie counterpart knows that there definitely will be parts or scenes from the book that will be removed. The same was true for the Lord of the Rings movie. Aside from the parts in the book not present in the movie, the creators of said movie also made changes to the story. The director believed that it was best to center the movie to Frodo and the ring to establish the movie’s “backbone”.
In addition, several descriptive events from the book were negated or somewhat changed in the movie. One example is the explosion of Sauron when in the book it says that his spirit only flees from his body.