Common Modal Verb Errors If workers are sick, they must to stay home and rest. ✖ incorrect] If workers are sick, they must stay home and rest. ✔ [correct] In this way children can learn from what they have done. ✔ [correct] In this way children can learning from what they have done. ✖ [incorrect] Common errors when using English modal verb structures The following modal auxiliary verbs are followed by the infinitive without to: can , could , may , might , must , shall , should , will , would : When travelling, we should respect the customs of the countries we visit. (NOT should to respect ; should respecting ) Modal verbs form questions and negatives without using do: Can I help you? (NOT Do I can help you? ) Will you meet me when I arrive? (not Do you will meet me… ) You mustn't worry about me. (NOT You do not must worry about me .) When we talk about obligation or necessity using have or need , we use to + infinitive : I have to finish my assignment this we