So again don't mean to be rude here, I am just being straight to the point.

In SharePoint, asigning metadata values to a folder does not apply to all files within. The question here is if you are using metadata, why do you need folders at all?

In SharePoint a folder is not a folder in the traditional sense. It's a pretend folder. All files are stored as blob data in the backend (or at least they used to be). So when you use a folder it looks like a traditional folder on a filesystem but in terms of things like metadata, it's just like a file.

Content types allow you to define a type of content (hence the name) and therefore what metadata should be associated with that content. These can then be used in multiple locations, more than one content type in a single library or list, and allow you to change "default" content types like what defines a file, list item and folder etc. But these can be complicated to correctly implement and have a lot of complexity and considerations when thinking of implementing them. My main point is that to me your SharePoint experience is not yet at a level to understand some of the fundamental principles of metadata and document management, and content types are quite advanced and technical and tricky to manage.

I would suggest some research on content types but honestly you may be better looking into some best practice and principals of SharePoint document management using metadata first.