The paper provides an overview of spectral and modal analysis methods for studying the stability of electric power systems (EPSs) and their control. Consideration is given to theoretical grounds of the methods and to the experience of their application for detecting the heterogeneity of the systems’ structure, identifying the coherency of generators’ motion, simplifying the mathematical model of the dynamics of EPSs, assessing their small-signal stability, and selecting the control actions to ensure it. The analysis of sub-Gramians for studying the EPS stability and other new directions in the development of the modal approach are discussed.