"This is the generation of the great LEVIATHAN, or rather, to speak more reverently of that mortal god, to which we own under the immortal God, our peace and defense." -Thomas Hobbes: Leviathan
There are two ways to understand the study of “metaphysics”.
The creatures which inhabit the “traditional” metaphysical world are familiar to most with some knowledge of philosophy, there are substances, accidents, forms and universals, (immaterial) souls and matter (not mass), habits and virtues and being and beauty and knowledge. This sort of metaphysics is evidently outdated and has little explanatory value.
To understand “modern” metaphysics, we begin first with the creatures which inhibits the world of physics. There are protons, electrons, quarks and elementary particles. There are gravity, curvatures in space-time, forces, energy and masses, electric fields and probability clouds. From these are derived the stuff of chemistry which are straight forward and simply derivatives of quantum mechanics, and from chemistry, biology. For convenience, I shall simply lump everything in biology, chemistry as simply “physics” simply because they are direct derivatives of physics.
However, besides the creatures of physics, there are also other entities. There are first-order logic, sets, functions, complex and real numbers, topology, lie groups, tensors and geodesics. There are centres of gravity (remember, a centre of gravity is a point in space-time but it is not itself a particle, force or field or whatever, it is, properly speaking an abstract entity), algorithms, software programs, databases and information processing systems, computation power, languages and syntax, musical compositions, novels, propositions, sentences, etc. Then there are economic classes and systems, societies, cultures and races and obligations and responsibilities, etc. Some of them cannot be derived from the creatures of physics, (e.g. the creatures of mathematics, although some parts of physics, like General Relativity, are said to be simply reducible to geometry), others are “supervenient” or emergent upon the creatures of physics but are more than the sum of their parts, e.g. human societies, economic systems, etc. A society is not just a collection of individuals.
Therefore if we go by the strict definition of “physics”, as I have defined it, then all the other entities I have listed in the previous paragraph are strictly “metaphysical”, not the creatures or entities of physics. There are more things in heaven and on earth than are contained in physics. Thus, basically, every entity outside of the field of “physics” is meta-physical.
While we can live without “traditional metaphysics”, but a world without “modern metaphysics” is impossible.