This document discusses the use of progressive verb forms with modals to express degrees of certainty or possibility. It provides examples of using modals like "may", "might", "could", "must" with the present and past progressive tenses. For example, "She might be getting better" or "She might have been sleeping". It also discusses using the progressive form with "should" and "ought to" when giving advice or referring to past counterfactual situations, like "You should have been listening while the teacher was talking!".