Modals

• Modals also known as modal verbs or modal auxiliaries,
• Modal express the speaker's attitude towards the action or state described by the main verb.
• No Inflection: Modals do not change form according to the subject.
• Use with Bare Infinitive: Modals are followed by the base form of the main verb (the infinitive without "to").
• No "Do" Support in Questions/Negatives: When forming questions or negatives with modals, the auxiliary "do" is not used.
• Can is used to express ability in the present, to express general possibility, and to give permission in an informal context. ​
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  Could is used to express ability in the past, to express a possibility that is less certain than "can" or to suggest something that might happen, and to be more polite or formal in asking for permission
• Might is rarely used for permission in modern English, though it can suggest a more tentative or less formal request. It is also used to express a weaker or less certain possibility, and used when making a polite suggestion or recommendation.
• Should is used to give advice, make recommendations, or express what is expected. Indicates something that is desirable or correct, but not obligatory.
• Must indicates strong obligation, necessity, or a logical conclusion. Used when something is required or essential. ​

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• Would is used to express a conditional mood, polite requests, or future in the past. Indicates willingness or habitual actions in the past.​
• Have to is used to express necessity or obligation. Similar to "must" but is more commonly used in informal speech.​
• Ought to is used to express a strong recommendation or moral obligation. Similar in meaning to "should," but slightly stronger.​

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• May is used to express a possibility, often stronger than "might'', to give or ask for permission, often in a more formal context, and to make a stronger suggestion than might