This paper presents a tri-band antenna that can be used for WLAN and 5G. The designed antenna consists of two L-shaped patches, metamaterial polygonal resonant ring and a defective ground structure. The high and low frequency bands are both generated by the L-shaped patch excitation. In addition, the defective ground structure improves the bandwidth of the high frequency band, and the loaded polygon resonant ring generates the middle frequency band. The experiment shows that the antenna can cover 3 bands of 2.27GHz-2.62GHz, 4.4GHz-4.8GHz and 5.3GHz-6.8GHz, which can be used for 2.4Ghz, 5.8Ghz of WLAN and 4.5Ghz of 5G. The results obtained have validated the potential of this design of a tri-band antenna for wireless communication.