Modal verbs are a small group of verbs which convey the speaker's opinion about or attitude towards what is being expressed. Modal verbs include ‘could', ‘should', ‘might' and ‘may'.
The modal verb ‘must' can express a speaker's sense of obligation - ‘I really must finish that project' - and how probable a speaker thinks something is - ‘You must be feeling awful'.
In the classroom
Modal verbs are problematic for learners for various reasons. They can have various uses and irregular negative and past forms. For example, the past of ‘must' depends on its function and can be either ‘had to' or ‘must have'. Exploring examples of the use of modal verbs from authentic texts will help learners build their confidence in using them.