Never experienced missing time myself but the metallic taste thing keeps coming up in poltergeist cases too, which is worth noting. A few witnesses I've spoken to over the years described it right before significant activity kicked off - not just UFO stuff, more like a general precursor to something anomalous happening in the environment.
There's a theory in some of the older literature that it's related to electromagnetic field fluctuations affecting the nervous system. Your fillings and the soft tissue in your mouth can actually act as a kind of antenna in strong EM fields, which could explain the taste. Persinger's work on temporal lobe sensitivity touches on this if you haven't read it.
What I'd want to know is whether you had any other physical sensations around the same time - ringing in one ear specifically, pressure behind the eyes, that sort of thing. Those tend to cluster together in accounts I've gone through and it might help narrow down whats actually happening physiologically. Anyone else got data points on this?