The document discusses modal verbs in English. It defines modal verbs as special verbs that indicate modality and lists some common modal verbs like can, may, must. It explains how modal verbs are used without conjugation and followed by the base form of other verbs. The document provides examples of different modal verbs and how they express ideas like ability, permission, possibility, obligation and advice. It discusses the forms of modal verbs and how many cannot be used in all tenses. Finally, it includes exercises for readers to practice using modal verbs.