Nanotechnology has become one of the most promising technologies. Metal nanoparticles have shown great application potential in the food industry owing to their unique physicochemical properties. This paper presents a systematic review of the methods used to synthesize metal nanoparticles, including physical, chemical, and biosynthetic methods. Special focus is placed on the mechanism, advantages and problems of the biosynthesis method as a green alternative approach, and the characteristics of the three methods are compared. The techniques used to characterize metal nanoparticles are summarized. The application of metal nanoparticles in the fields of food preservation, rapid food safety detection, and functional food additives is discussed at great length. Finally, the challenges and future trends in the wide application of metal nanoparticles in the food industry are specified. This review aims to provide a systematic theoretical reference and guidance for the green preparation of metal nanoparticles and their efficient and safe application in the food industry.