Massive multiple -input multiple -output (MIMO) technology offers significant improvements in both spectral and energy efficiency by utilizing the same time and frequency resource as current radio networks to simultaneously serve multiple users with the use of channel state information measurements and linear processing schemes at the base station. These remarkable gains are obtained by equipping each base station with an array of many (hundreds or thousands) antennas to enable spatial multiplexing of many user terminals. The performance analysis of massive MIMO relies on its fundamental properties comprising the channel hardening, the favorable propagation, and the sparsity. This chapter presents some well-known channel models used in massive MIMO and evaluates their corresponding fundamental properties.