Thermal ablation is increasingly utilized in the treatment of primary and metastatic liver tumors, both as curative therapy and as a bridge to transplantation. Recent advances in high-powered microwave ablation systems have allowed physicians to realize the theoretical heating advantages of microwave energy compared to other ablation modalities. As a result, there is a growing body of literature detailing the effects of microwave energy on tissue heating, as well as its effect on clinical outcomes. This article will discuss the relevant physics, review current clinical outcomes and then describe the current techniques used to optimize patient care when using microwave ablation systems.