This chapter addresses the critical need to enhance the resilience of transmission systems in power grids, particularly in the face of increasing extreme weather events and the growing threat of cyberattacks. It emphasizes the vulnerabilities of traditional electricity infrastructure and calls for a shift toward resilience-focused planning. Resilience in power systems is defined through a framework involving proactive robustness, real-time event management, and rapid restoration. This chapter proposes two fundamental models: a Markov model for managing weather-related risks by developing proactive generation re-dispatch strategies that minimize load loss and a dynamic game-based model for cyberattack scenarios that explores the interactions between system operators and intruders, considering compromise probabilities, costs, and system impacts. Both models highlight the importance of adaptability in managing unforeseen events. This chapter concludes by emphasizing the need for sophisticated restoration strategies, particularly in generating unit start-up algorithms, and calls for enhanced coordination and flexibility in restoration planning. This work highlights the importance of resilience as a core principle for future power system design, ensuring critical infrastructure stability and rapid recovery.