The abstract syntax of UML is specified using a UML model called the UML metamodel. Classes in a metamodel are called metaclasses. The detailed descriptions of each metaclass are provided in the UML specification.pdf.
The metaclass icon in the Model Browser is 
. Its shape is displayed with <metaclass> stereotype.
All metaclasses in our modeling tools are stored in the Auxiliary Resources, expand the UML Standard Profile Package > UML 2 Metamodel Package.
To show the auxiliary resources
- In the Model Browser, click
and enable the Show Auxiliary Resources option.