Do is one of three auxiliary verbs in English: be, do, have. We use do to make negatives (do + not), to make question forms, and to make the verb more emphatic. …. Do as an auxiliary verb: typical errors. We don’t use auxiliary do to make questions or negatives for clauses with modal verbs: …. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.