Crystalline microporous aluminosilicates, zeolites, are attractive catalysts and adsorbents in industrial and fundamental research fields. Their Brønsted and Lewis acidities are one of the most important features of their application. Moreover, zeolites can be modified with various metal incorporations from the perspective of new functions. Herein, we discuss the properties of zeolites modified with various metal species with different loading states (incorporated into framework and non-framework positions). The structural and compositional features of their active sites and parent zeolites, and the catalytic and adsorptive properties of metal-modified zeolites are summarized based on their application fields.