You can insert videos in your presentations to add a little flair and emphasize your point. Just make sure to keep the videos short, so that they don't become the main event.
Videos that are inserted from a file are embedded directly into the Slides presentation, so the presentation file size will increase when videos are inserted.
The Insert video dialog box opens, giving you a few ways to add a video to your presentation.
If you want to search YouTube for a video, you can do that here. Otherwise, you can paste the URL of a specific YouTube video, or insert a video that you have saved to your Google Drive.