In modern societies, political debate happens largely on social networks, which makes opinion dynamics models especially valuable for their descriptive and predictive power. Understanding how opinions form and change online can help keep public discourse healthy and protect the democratic foundations of our increasingly digital societies. This master's thesis explores opinion dynamics in complex social systems, with a particular focus on the role of leaders and their interaction with external events. To this end, we based our approach on Heider’s social balance theory. This latter is well documented in the literature, but the connection between micro-level balancing processes and broader network dynamics has received limited attention in existing research.