They are generally filled at some point or indicate reversal like island reversal. although you could also have a breakaway gap. Many times, a good purchase point would be at the high of the day before the gap occurred.
Pullback makes the next move stronger and gives me an opportunity for day trade longs so I don't have to chase the market.
If TIME-BASED FASTER THAN A DAILY, if/when the chart is configured to RTH (or whatever start and end times are equivalent to a daily bar), opening gaps can be seen, annotated, defined, and most importantly, used by traders.
I wish somebody would have told us in advance that the direction is about to change. Oh wait... OK, I was 10 points and a day early, but here we are 20 points below the quoted top call with the bearish island reversal...
Actually it is. You may recall that what I desired was a fallback to the 2675-2680 line and then gather steam for a further upmove.