This chapter introduces EM field computational methods. We begin by covering the fundamental concepts required for 3D field computation, including the computational mesh used for discretizing the simulated geometry. We also discuss mesh adaptation techniques and the metrics used to evaluate mesh quality. Next, we introduce basic material models commonly used in EMC simulations, comparing their applicability. Additionally, we present more advanced models that account for dispersion and nonlinear material behavior. Following this, we provide an overview of the boundary conditions necessary at the boundaries of a computational domain. We then examine different source types in an EM simulation model and explain how field results can be converted into circuit-based quantities. After highlighting common pitfalls in EM simulations, we discuss various full-wave methods in both the time and frequency domains, comparing their performance across different application scenarios. In the advanced section of Chap. 4 , we demonstrate how Maxwell’s equations are discretized in both time and space for different full-wave methods.