In recent years, affected by the factors, such as the U.S.-China trade war, COVID-19, etc., the human resources and costs have increased the uncertainties of the production line. To reduce the production risks in metal manufacturing industry, some companies, such as Boeing, Pratt & Whitney, are gradually upgrading their production lines through the technologies of digitization and intelligence. Machine tool is important for the production of metal components, and its digitalization is a critical factor for intelligence upgrading. Therefore, the developments of machine tool digital twins have become the focus in several research groups all over the world. In this article, the current research status of self-organizing digital twins for machine tools will be focused. The digital models of key components (such as spindles), online monitoring, and the artificial intelligence-based system integration will be introduced. Finally, its applications will also be discussed.