PRINT http://www.teach-this.com/images/resources/the-modal-hotel.pdf http://www.teach-this.com/images/resources/when-you-were-a-child.pdf http://learnenglishteens.britishcouncil.org/grammar-vocabulary/grammar-videos/have-must-and-should-obligation-and-advice http://linguapress.com/grammar/modal-obligation.htm http://www.perfect-english-grammar.com/modal-verbs-of-obligation.html http://www.englishgrammarsecrets.com/musthaveto/menu.php Modal verbs of obligation : must, have to, should and ought to There are two types of modal verbs of obligation ; those that primarily express a firm obligation or necessity - must and have to those that express a recommendation or moral obligation - should and ought to Firm obligation, etc. - must and have to The verb must only exists in the simple present and present perfect forms. While the present form can express obligation, necessity, certainty or strong probability , the present p