This book provides a comprehensive and self-consistent introduction to the field of plasmonics and metamaterials. It starts with a brief introduction and description of the motivation behind writing the book. Then the authors summarize the basic theory of the conventional spoof surface plasmon polaritons including propagating and localized spoof SPPs, conformal SPPs, ultrathin localized spoof SPPs as well as their applications. Next, dielectric-based spoof surface plasmons and related applications are discussed. Later, the structural dispersion induced effective surface plasmon polaritons and localized effective surface plasmon polaritons are illustrated. Following this, the authors give a basic idea and applications of non-linear spoof surface plasmon polaritons and localized spoof SPPs.