The article reviews different models of how money works in the economy. These models try to understand how money affects the economy and how it can be used to make policies. Some popular models include money-in-the-utility function, cash-in-advance, overlapping generation, search model of money, and new classical model of money. While these models may not fully explain the relationship between money and the economy, they help us study how money works and its impact on policies. The new classical models of money show us where to focus our future research on monetary theories.