A design and performance analysis of a metamaterial (MTM) based rectangular microstrip patch antenna (RMPA) with four dual isosceles triangular defects on the metallic ground plane have been presented in this paper. At first, a conventional RMPA is designed by using Isola FR-408 (lossy) substrate material (ε r = 3.75 and tan δ = 0.0013). After that, the RMPA with four dual isosceles triangular defected ground structure (DGS) has been designed and verified as metamaterial with the help of Nicolson Ross Weir (NRW) method. Professional CST software has been used to perform the simulation of the designed antennas. The bandwidth of the proposed metamaterial antenna is enhanced by 345.71% compared to our designed conventional RMPA (105 MHz for conventional RMPA and 468 MHz for metamaterial RMPA), return loss is reduced from -23.10 dB to -44.299 dB, gain is enhanced from 0.205 dB to 6.291 dB, directivity is increased from 5.179 dB to 9.314 dB and voltage standing wave ratio (VSWR) is of 1.0123 which indicates very good VSWR.