The next generation of mobile systems based on LTE-A (Long Term Evolution-Advanced) networks are expected to support the new promising technology M2M (Machine-to-Machine) communications while keeping an eye on its previous H2H (Human-to-Human) communications not to be affected especially when it comes to the expected exponential growth of the number of M2M in the coming years, in particular, with the advance of IoT (Internet of Things) deployment and the expected ubiquity of such objects in the near future. In this article, we review the M2M communication technology from the LTE-A perspective and we outline the random access challenges in high dense areas where the LTE-A network is striving to fulfill the massive number of M2M devices. Moreover, we compare the most common mechanisms found in the literature that deal with the RACH (Random Access Channel) procedure issues and challenges by analyzing the existing solutions and approaches to avoid RACH overload congestion in the M2M communications. To this end, we have developed different M2M scenarios using SimuLTE Modeler to investigate the impact of M2M communications on LTE-A networks in emergency events.