When alkali metals are loaded into nano-space of zeolite crystals, cationic clusters of alkali atoms are stabilized there. The s-electrons of alkali atoms are shared with many other alkali atoms in cages, and occupy quantum levels, such as 1s, 1p, etc. These s-electrons in clusters show novel properties depending on the structure of clusters, quantum mechanical effect on s-electrons, Coulomb interaction between s-electrons, degeneracy of 1p orbitals, spin-orbit interaction and also the intercluster interaction. In K-loaded K-form zeolite LTA, ferromagnetic properties are observed depending on the average loading density of guest K atoms, although no magnetic element is contained there. Metal-to-insulator transition occurs when alkali metal is changed from K to Na in zeolite FAU, where Na and K clusters are in Mott insulator and strongly correlated electrons, respectively. Observed electronic properties are closely related to the structural properties of alkali atoms in the zeolite regular cages, such as superstructures.