Is it possible to add custom fields in metadata for site and lists of MS Share Point?

[FFB01]

We have a requirement to associate custom metadata while creating site or lists. We tried exploring the SharePoint documentation and were able to add this for List items, folders and files but did not find any reference of it for Site or Lists. Could you please let us know if this is possible to add custom metadata while create a new site and new List

[#2]

The concept of metadata at the site or list level does not exist...the most similar thing you can have in SharePoint to that metadata concept are the property bags

[#3]

@Juan Carlos González Martín ,

Custom Metadata in terms of SharePoint means, Custom Site Columns and Custom List Columns that SharePoint allows users to create.

[#4]

I know what metadata means in the SharePoint world (I've been working there for the last 14 years) ;) and what I say is correct...you can create your site columns, but you can only use them in lists and document libraries. So no sure what's your question here