In recent years, rapid advances in different energy technologies and emerging new intelligent systems have driven energy networks to undergo an unprecedented deformation. In the path of this transformation, some critical challenges have appeared regarding the handling of a large number of new smart devices, ensuring their fit with society's requirements, raising dependences among multifarious energy grids, ever-increasing in multi-vector energy consumption, etc. One of the key phases of this evolution is related to the huge need for growing the penetration of renewable energy resources (RERs) in response to an unacceptable range of pollution created by conventional energy suppliers. However, how the current potential of an upgraded system can allow for the exploitation of numerous RERs and effectively handle their presence is a key challenge requiring innovative solutions and practical strategies. The modernization of energy networks addresses the need for building a reliable, secure, resilient, and intelligent network that enables the system with a full/high share of RERs for sustainability while allowing end-users to benefit from more and greater diverse market services and opportunities by actively participating in the energy grid's interactions. This chapter clarifies what are the characteristics of future modern energy networks and why grid modernization is essential for the interdependent structure of networks that are going to be engaged with a large number of stochastic clean energy production devices. The related challenges and opportunities are also targeted to be covered to give a clear overview for the future modern multi-carrier energy grid.