In short, metaphysics is the philosophical study of being and knowing. As this site explains, “if you have ever contemplated your own existence in the universe, you were dabbling in metaphysics.”
The word metaphysics derives from the Greek works “meta ta physika” and came to be known as a field of inquiry that seeks to understand “the science of things transcending what is physical and natural,” such as the existence of God or the origin of human knowledge. Metaphysics relies on philosophical logic, rather than scientific experiments, in exploring these questions.
From this short explanation, it should be obvious how disparate can be the metaphysics of the world’s many “believers” – be they Christian, Hindu, atheist, New Age, pagan, etc.
For example, Christians believe in one God. Hindus and pagans believe in millions of gods. Atheists believe in no gods and New Agers believe we’re all gods.
According to David Noebel in Understanding the Times: The Collision of Today’s Competing Worldviews, Christian metaphysics is clearly spelled out in Scripture: “In the beginning [of the cosmos] was the Word [Logos, mind, reason, thought, wisdom, intelligence, idea, law, order, purpose, design], and the Word was with God, and the Word was God. The same [Word] was in the beginning with God. All things were made by him; and without him was not anything made that was made. In him was life; and the life was the light of men” (John 1:1–4).
Catholic metaphysics is also spelled out very succinctly in the Catechism which explains that God is “the first principle and last end of all things ….” (No. 36) meaning that He is the cause of all things and the end toward which all is moving. This is why He is “the master of history . . .” (No. 269).
It’s always important to understand the metaphysics belonging to the various belief systems in order to discern what is compatible with Christianity and what is not.