Looking at the Metropolis...it doesn't seem to clock multiply, only divide. So, if you're sending it an 8th-note pulse, that's your minimum rhythmic value. In order to get the sequencer to step at 16th-notes, you're going to have to use a clock multiplier to half the time on the 8th-note pulses, or just feed a 16th-note pulse as your master clock and then use clock dividers to obtain lower values where needed.