Modal verbs are a special type of auxiliary verb in English grammar. They express modality, which includes concepts like possibility, necessity, permission, ability, and other attitudes toward actions. The most common modal verbs include can and could for ability and possibility, may and might for permission and possibility, will and would for future actions and willingness, shall and should for obligation and advice, and must for necessity and strong obligation.
Modal verbs serve several important functions in English. They express ability and possibility, as in 'I can swim' or 'It might rain'. They're used for permission and requests, like 'May I use your phone' or 'Can you help me'. Modal verbs also indicate obligation and advice, such as 'You must wear a seatbelt' or 'You should study harder'. Additionally, they express future actions and willingness, as in 'We will meet tomorrow' or 'I would like to help'.
Modal verbs follow specific grammar rules. First, they are always followed by the base form of the main verb, without 'to'. For example, 'She can speak English', not 'She can to speak English'. Second, modal verbs never change their form - they don't add 's' in third person singular. We say 'He can swim', not 'He cans swim'. Third, questions and negatives are formed using the modal verb directly, without auxiliary verbs like 'do' or 'does'. We ask 'Can you help?' not 'Do you can help?'
Modal verbs often come in pairs with different meanings and levels of formality. Present forms like 'can', 'may', and 'will' have past or conditional forms: 'could', 'might', and 'would'. There are also formal and informal variations - 'may' is more formal than 'can' for permission, and 'shall' is more formal than 'will'. Modal verbs also vary in strength of meaning. 'Must' expresses the strongest obligation, 'should' gives advice or recommendations, while 'could' and 'might' express weaker possibilities.
To summarize what we have learned about modal verbs: They are auxiliary verbs that express modality including ability, permission, and obligation. Modal verbs are always followed by the base form of the main verb and never change their form. They vary in formality and strength of meaning, making them essential tools for expressing attitudes and relationships in English communication.