The aim of the doctoral thesis is to investigate the strategic behavior of participants in modern electricity markets and to analyze the dynamics that shape prices in conditions of energy transition. Due to market liberalization and the rapid penetration of Renewable Energy Sources, there is a need for a deeper understanding of the decisions made under conditions of uncertainty and competition. In essence, the study examines how the interaction of market factors affects overall efficiency and social welfare. The main objective is to highlight the mechanisms of bid formation and to assess the role of regulatory policy in limiting the exercise of market power and ensuring the smooth functioning of electricity markets.