Putting its rather arbitrary etymological origins to one side, we can say the word ‘metaphysics’ refers to the philosophical study of reality: metaphysics essentially attempts to establish a coherent picture of what reality ultimately is and how reality ultimately works.
In doing so, it explores basic issues around substance, existence, causality, determinism, modality, ontology, possibility, and nothingness — most of which are discussed by Aristotle in those initial writings grouped by Andronicus, but also by philosophers throughout history.