This source focuses on expressing necessity through the use of the modal must and the phrasal modals have to and have got to. While all three convey that something is required or there is no other choice, they differ in tone and context.
Key Modals for Necessity
Must: This is typically stronger than the other options and indicates urgency or high importance. It is most commonly found in formal rules, legal information, written instructions, or when adults speak to young children about rules.
Have to: This is the most frequently used form in both everyday speech and writing. Unlike must, it is the standard choice for asking questions about necessity.
Have got to: This is an informal expression used primarily in spoken English. In speech, the "have" is sometimes dropped (e.g., "I gotta go")
