Nowadays, the forms of energy generation, transportation, utilization, and application are changing all over the world. Given the significant penetration of intelligent systems in human society as well as modern energy distribution systems globally, smart grids are effectively developed to integrate various innovative technologies aiming to improve energy supply process. The array of these technologies has formed widespread efforts to ensure the satisfying of modern living standards that have led to the grid modernization process. In this regard, modernizing the future multi-carrier energy networks is essential for effectively handling the widespread presence of the numerous advanced technologies and intelligent systems in the network place. This chapter is targeted to analyze the role of electricity, natural gas, heat, and water networks in the modernization of the multi-carrier energy networks. Also, this chapter responds to this key question that why we need grid modernization by evaluating different aspects of the future modern grids. Finally, this chapter focuses on various energy markets and structures to give a superlative viewpoint of the future energy markets with the aim of laying the groundwork for energy market development in the modern power system landscape.