The COVID-19 pandemic has severely affected people's daily lives and caused tremendous economic losses worldwide. AI technologies have been employed to fight the disease and predict the disease spread. However, its impact on human behaviors, e.g., public opinion and mental health, has not received as much attention to inform the policy and decision makers. Traditionally, the studies in these fields have primarily relied on interviews or surveys, largely limited to small-scale and not-up-to-date observations. In contrast, the rise of social media provides an opportunity to study many aspects of a pandemic at scale and in real-time. Meanwhile, the recent advances in machine learning and data mining allow us to perform automated data processing and analysis. We will introduce several case studies, including 1) nuanced opinions on COVID-19 vaccines, 2) depression trends, 3) attitudes towards work from home, 4) consumer hoarding behaviors, 5) personal face mask usage, and 6) what to blame for inflation,