Monism is the view that reality consists of one fundamental, ultimate essence. It comes from the Greek mono, which means one. All is one. Therefore, in monism God and the universe are the same thing. This would mean that energy, motion, matter, thought, consciousness, etc., are all of one substance but are perceived differently.
Monism stands in opposition to the dualism and pluralism but is often defined the same as pantheism, the teaching that God and the universe are the same thing.
Monism is unbiblical because it denies the distinction between God and creation.