Metaphysics is the hearth of philosophy. It deals mainly with two questions.
First: what is being?
A thing - the sun, the cup of coffee next to this computer, your father … - have many properties. Some of them they have in common, others are specific. One characteristic they all share is ‘being’: they all exist.
Now, there is a distinction between being (Sein) and a being (Seiendes in German, entity in English, zijnde in Dutch). Being is general: it is the property all things that exist - all beings, or entities - share. Entities are things, substances.
Here a problem arises. To express ‘being’ one always refers to entities. It is impossible to express being qua being; and so there is an inevitable reduction of the meaning of being, when one defines being. To express the general property of being that the sun shares with my coffee cup, one could say that they are both material. To be is to be material. But what does it mean to be material? It means: to be uniquely and determinately localizable in space. Materialism is the idea that if something cannot be localized in space, it does not exist. To be is to be in space; and space is an entity. In defining the being of entities I refer back (reduce to) another entity. This begs the question: what is the being of space? One cannot apply ‘to be is to be in space’ to space itself.
As far as we know, all definitions of being refer to beings; and thus fail.
Second: is there something real my representations correspond to?
Even though I cannot look directly at the sun, I have representation of it. Take somebody from the Middle Ages. He would probably agree with some of the properties you or I would attribute to that entity. It is yellow in colour. It gives light and warmth. The man or woman from the Middle Ages would probably also claim that the sun revolves around the earth. We would disagree. To verify who is right, we could take a closer look. We all jump into a spaceship and fly into space. We would then all have to agree that the sun is actually at the centre of the solar system.
The idea that the sun revolves around the earth is based on a representation. Our new representation contradicts the first one. But it is itself again a representation. Every new representation begs the question: how does it correspond to reality? To verify our new representation one could refer to light travelling from an object to our eye. No matter how plausible, this too is again a representation.
Conclusion
Both questions are unanswerable. When somebody claims to have an answer to one or both of these questions, he is called a metaphysicist. That is meant as an insult.