The renewable resources are expanded to replace the power plants with high carbon intensity, such as coal plants. Gas-fired power plants are the main linkage between these two networks. Due to their characteristics, such as fast ramping rate, these plants complement the lack of renewables, and hence the intermittent nature of RES in the power system will be reflected in the gas network demand. As a solution, flexibility options, such as storage systems, bidirectional compressors, and power-to-gas (P2G) systems, are employed to cope with the imposed intermittency to the energy system. Taking into account the proposed issues, in this chapter, different types of flexibility options are firstly introduced, including their uses and mathematical models. After that, the contribution of these components in mitigating the intermittency and variability of RES is investigated based on previous projects and studies.