As energy systems become more complex, the need for innovative technologies to manage and optimize their performance is critical. The integration of Digital Twin (DT) technology into Internet of Things (IoT)-based energy systems offers a novel approach to improving resource management, sustainability, and operational efficiency. While existing studies have explored various aspects of DTs in energy systems, this chapter focuses on the specific convergence of DTs and IoT infrastructure in emerging smart energy systems, emphasizing their role in optimizing energy efficiency, production, consumption, and storage. Through a comprehensive review of recent literature, we analyze the distinctive applications of DTs in areas such as real-time energy monitoring, predictive maintenance, and enhanced grid management. Additionally, this chapter distinguishes itself by examining the current research trends, key technological advancements, and the unique challenges associated with deploying DTs in IoT-driven energy ecosystems. Our review provides a thorough understanding of how DT technology can transform smart energy systems and offers insights into future research directions.