Simulating microwave cavities can prove to be difficult. The size of the cavity itself, the resonant nature of the cavity, and the number of total modes can all contribute to issues in microwave cavity modeling. In industrial applications, a microwave cavity and feeding system design needs to maximize the delivery of microwave power to a predetermined volume of space. Controlling the power distribution is also key as it ensures heat uniformity. In scientific applications, well-defined distributions of the E-field or B-field is more of a priority. Regardless of what the application is for, reliable modeling and performance simulation is key. This white paper discusses the modeling of microwave cavities and demonstrates how a system for heating test samples was optimized using electromagnetic simulation.