This summary on Christian metaphysics and Platonism is from the Introduction to Four Views on Christian Metaphysics.
Platonism as an approach to metaphysics is a form of dualistic realism. First, it maintains dualism. There are two parts to reality, physical and non-physical reality. Further, for Christian forms of Platonism, there is a dependency of the existence of physical reality on non-physical reality, specifically on God. Second, Platonism maintains realism. Both physical and non-physical reality are real, and independent from human cognition. There are different versions of Christian Platonism, but in general it will maintain that existence is found ultimately in God, that universals are real and related to God, that the soul has two parts (body and mind) and that all of these things are sustained in existence by God.
I recommend obtaining a copy of the book and reading Chapter 1. The outline for the chapter is as follows:
1.1 Platonism – Paul M. Gould
1.2 Aristotelianism Response – Timothy L. Jacobs
1.3 Idealism Response – James S. Spiegel
1.4 Postmodernism Response – Sam Welbaum
1.5 Platonism Reply – Paul M. Gould
~ Boethius ~