The answer to the question is in the charts. If gaps can be seen, which were not filled, then not all gaps must be filled.
Some markets have more gaps than other markets. Gold is a global market and rarely has gaps at the daily chart level, but it may have gaps occasionally at the hourly chart level and below.
The S&P500 is a good example of a market with gaps.
There are two examples of gaps not filled in the daily chart above for the S&P500, from price movement during February of 2017. To this day, 8 months later, these gaps remain unfilled.
Published @ 05:10 p.m. EST.