The logical frameworks based on a constructive type theory will be discussed as the paramount example of a metamodel where you can factor out tools for building systems from manipulating the other systems.
But there are more in the plethora of calculi for concurrency . We have the "action structures" of Millner, we have the "rewriting logics", we have "graph-grammars", and we have many different kinds of double and reached categories. Just to mention one, the "tiles" of Montanari.