Trigger repeated actions metronomically

The metro (metronome) object is the most obvious way to trigger repeated events in Max. Repetition is, of course, a key component of most music (and most time-based art in general), and the metro object encapsulates the whole low-level process of a) cause something to happen, b) schedule the same thing to happen at some future time and repeat the process. The only thing it needs to "know" is what time interval to use for its repetitions.