The usage of carbon monoxide (CO) as a C1 feedstock for carbonylation has been an important subject of numerous studies for over a century. The chemistry in this field has evolved significantly, and several processes (e.g., Fischer-Tropsch, Monsanto, and Cativa process) have even been industrialized to serve humankind in our daily lives. CO is also a crucial ligand (carbonyl) in organometallic chemistry, and transition-metal carbonyl complexes have been widely used as homogeneous catalysts in various chemical transformations. Historically, transition-metal carbonyls have been considered to be dominant for these purposes. In recent decades, main-group elements, especially naturally abundant elements in the Earth's crust such as silicon and aluminum, have gained much attention, as they are eco-friendly and have low toxicity compared to the late transition metals. Recent developments in main-group chemistry have revealed reactivity which can mimic that of transition-metal complexes toward small molecules such as H2, alkenes, and alkynes, along with carbon monoxide. This Perspective highlights CO activation by main-group compounds which leads to the formation of carbonyl complexes or CO insertion into the main-group element center as well as the reductive homologation of CO.