Ultra-short pulse laser bursts have attracted a lot of attention in industrial micromachining due to their advantages over conventional laser modes, especially their high ablation efficiency. In burst mode, the single pulse is replaced by a package of several pulses with the same total energy. Burst-mode lasers usually operate at different repetition rates, either in the MHz or GHz range, corresponding to nanosecond and picosecond intra-pulse delays, respectively. Our experimental focus is on measuring the ablation efficiency as the material ablated per fluence. We have investigated the ablation efficiency when drilling thin metal foils in MHz burst mode. We have investigated how this efficiency depends on the variation of different parameters, including the laser wavelength (1030 nm or 343 nm), the material of the foils with different thicknesses, the pulse durations (300fs - 10ps) and the number of pulses in the bursts. In addition, the results obtained are compared with those obtained with ns pulses at pulse durations corresponding to the total burst durations. Further analysis of the drilled holes using SEM images of the entrance and exit of the holes as well as the cross sections of the holes (generated by a focused ion beam and by polishing) explains the role of the remolten material at a higher number of pulses within the burst. Our results demonstrate the potential of MHz bursts as a viable and cost-effective alternative to GHz bursts for wider use in industrial applications such as laser drilling and micromachining.