Recent advances in wireless communications and electronics has enabled the development of machine-to-machine (M2M) communications. This communication paradigm has been expected as an automated control and report solution for smart grid. The smart grid enables customers and operators to utilize the collected usage information from a large number of meters with transceivers for efficiency and safety. In this paper, we introduce architecture, requirements and challenges of M2M communications for smart grid. We extract technical issues that should be resolved in M2M communications to support the smart grid via third-generation partnership project (3GPP) cellular networks. We then present the current state of the art of research results to deal with such issues. Finally, we outline the open research issues.