Add or change a movie theme in iMovie on Mac
iMovie includes a number of Apple-designed themes—sets of visually related titles and transitions—that have a unique visual style and give your movies professional polish. iMovie can automatically add these titles and transitions as you build your movie.
You can apply a theme after you create your project. You can also easily switch themes.
In the iMovie app on your Mac, click Settings in the upper-right corner of the timeline, and then click the Theme button.
In the Change Theme window, do one of the following:
Choose a theme: Select a theme, and click Change.
To preview a theme, move the pointer over the theme’s thumbnail and click the Play button .
Remove the theme: Select No Theme, and click Change.
When you set or change the theme, you can also set iMovie to let you insert and edit transitions manually. For more information, see Turn off automatic transitions in iMovie on Mac.