Proverbs are short, well known sayings that express a common truth or belief. We often use them when we give advice. In your English class they can be used as an authentic fun material, as a tool to draw the audiance's attention at the start of a presentation. Learning them by heart helps pronunciation practice and they usually provide useful vocabulary.
Secret phrase that your learners will need to unscramble in this puzzle: There is no use crying over spilled milk.