This document provides information about modal verbs in English. It discusses how modal verbs do not have past or future tense forms and do not take an 's' for third person singular. It explains how modal verbs are used to change the tense or meaning of other verbs when speaking in the past or future. Some common modal verbs and their meanings and uses are defined, including examples. Key points covered are the uses of modal verbs for obligation, ability, permission, speculation, and deduction. Differences between modal verbs like can/could and must/have to are explained.