This book provides a detailed introduction to the basic metamaterial modelling approaches and an overview of innovative phenomena enabled by metamaterials. The book covers discussions on the fundamental formalisms used in the study of metamaterials comprising the ordered and disordered configurations of meta-atoms. It also illustrates the application of these in different directions, such as designing antennas and radars, multi-controllable sensors, perfect absorbers, tuneable devices, and biological sensors. This book provides a useful tool for both the current and future participants (academics and/or professionals) in the area of photonics by presenting methodologies for sustainable materials for energy harvesting and sensing, health diagnostics, meeting the needs of a range of readers from students to early career researchers to established scientists in their fields. Part of IOP Series in electromagnetics and metamaterials.