Normally, adding a background video to your homepage is a function that is supported by your current theme — or not.
Out of the box, the default WordPress theme does not include the ability to add a background video to your homepage. But, even if your theme doesn’t support this functionality out of the box, you can install a third-party like this one, which will enable you to easily add a video background to any element on your WordPress site:
Adding a video background to your homepage can help you capture your visitors’ attention, and it’s a very popular web design trend. But you should also consider that video files can be quite large, so adding a video to your homepage could significantly increase you page load times. And that can have an adverse effect on your search rankings in Google.
And, it’s not consider a best practice for accessibility, as many people are sensitive to motion graphics. Personally, we’d recommend avoiding this trend, unless it absolutely critical to your site’s brand.
Hope this helps!