This is a PowerPoint Presentation "Modal Verbs of Probability through the song -The day before you came". Recommended for adult students of the upper-intermediate level. I planned it as a whole lesson from the beginning to the end where all questions are given on slides. It's supposed to be an interactive lesson "teacher - students". First revise some modal verbs, then concentrate on "must" and work with it, comparing "present modal structure" with "past modal structure". Hope,some ideas will be useful.