Modal verbs can be tricky for learners to master due to their nuanced usage in expressing permission, obligation, and possibility. Some common mistakes learners make when using modal verbs in English include:

1. Confusing modal verbs with other auxiliary verbs: Learners often mix up modal verbs like “can,” “could,” “may,” “might,” “will,” “shall,” “should,” “must,” and “ought to” with other auxiliary verbs, leading to incorrect sentence structures.

2. Using modal verbs incorrectly for different purposes: Learners sometimes misapply modal verbs, such as using “may” for permission instead of “can,” or using “can” for possibility instead of ability.

3. Neglecting inversion with modal verbs: In English, modal verbs are often followed by the subject and then the main verb, leading to errors when learners forget to invert the subject and modal verb in questions or negative statements.

Errors in expressing permission, obligation, or possibility with modal verbs can often appear in the following ways:

1. Permission: Learners might mistakenly use “could” instead of “can” for present permission, or forget to use “be able to” for more formal contexts.

2. Obligation: Errors can arise when learners interchange “must” and “have to,” as “must” implies strong personal obligation while “have to” suggests external obligation.

3. Possibility: Confusion can occur between “may” and “might,” as “