You create the following types of relationships in Metadata Manager:

You can create relationships when you create a custom model, edit custom classes, or edit custom metadata objects. You cannot create relationships for classes or metadata objects in packaged or universal models.

For example, you can edit a custom metadata class and create a relationship from the custom class to the Oracle Table class. Alternatively, you can edit the custom metadata class and create a relationship to the custom class from the Oracle Table class. However, you cannot edit the Oracle Table class and create a relationship to or from any other metadata class type.