The document discusses the modal verbs can and cannot. It provides examples of affirmative sentences using can to express ability like "I can speak French" and cannot to express inability like "I cannot cook pizza." Negative sentences are formed by adding "can't" or "cannot" before the infinitive verb. Questions are formed using interrogative words before can/cannot and the subject plus infinitive verb. The modal verbs can and cannot are used to talk about ability and possibility.