This paper investigates the bandgap characteristics of inerter-based dual-resonator metamaterials and analyzes the low-frequency vibration suppression performance from the perspective of wave transmittance and vibration power flow. The studied metamaterial configuration is a one-dimensional mass-spring chain system with N identical lumped masses and each lumped mass has two resonators attached. Each unit cell of metamaterial is considered as a 1-DoF system with the effective mass varying with the excitation frequency, which can be negative in specific ranges of excitation frequencies. With dual resonators, dispersion relation diagrams show that there will be two separate bandgaps in which vibration transmission is suppressed, the frequency ranges for the bandgaps are similar to those for negative effective mass. Wave transmittance and power flow analysis also provides new perspectives to evaluate the dynamic characteristics. The results indicate that the wave transmittance is low and the energy is blocked within the bandgaps. The bandwidths of two bandgaps will not be influenced by cell position and the power transmittance of high excitation frequency is decreased as position number increases. The effect of inertance change on bandgap characteristics is examined and it shows that when the other parameters are the same, the two bandgaps are merged into one complete wide bandgap with identical inertance. These findings can provide a better understating of the dynamic behavior of dual-resonator metamaterials and their optimal design.