Cyanobacteria, which are widely distributed in nature, have acquired remarkable abilities to thrive under various conditions and have shown strong adaptability throughout their long evolutionary history. Extremely saline environments are one of the most common abiotic stresses, and cyanobacteria living in such environments must adapt their metabolic pathways to salt stress. This chapter describes the molecular responses of essential metabolic pathways in cyanobacteria to salt stress, including photosynthesis, carbon metabolism, nitrogen fixation and assimilation, P metabolism, and lipid metabolism. In particular, we provide an overview of findings at the transcriptional and translational levels in the model halotolerant cyanobacterium Halothece sp. PCC7418. Metabolic pathways are highly interdependent and are exquisitely regulated by factors such as enzyme activities and substrate concentrations. Here, we aim to understand how high-salinity environments have influenced the functionality and regulation of universally present primary metabolic pathways in living organisms.