Metadata you assign in Lightroom is stored in the Lightroom database. You can't store this metadata in the video files.
It's been over four years since video was added to LR. The support for video metadata was incomplete and buggy, and little has changed since. Please add your vote and opinion to this topic in the official Adobe feedback forum: Lightroom: Metadata applied to videos in Lightroom isn't available in other applications. Adobe product developers rarely participate in this forum here, but they are active in the official feedback forum.
I am referring to the metadata already present in the video files before they are imported in Lightroom. Upon import - to my opinion - at least the most basic metadata should become available as visible/usable metadata in Lightroom. Especially items available as file rename tokens, e.g. camera model.
I also don't understand why at least camera model is not working, for example iphone is not recognized.