Supposed to is used when we are talking about our obligations. Use supposed to when saying what is the best thing to do in a situation; the correct way of doing things. For example, use supposed to for cultural rules and expectations.

When can we use supposed to?

Supposed to is part of a modal verb phrase meaning expected to or required to. Although suppose to crops up frequently in casual speech and writing, it should not be used in that sense. Suppose (without the d) should only be used as the present tense of the verb meaning to assume (something to be true).

How do we use be supposed to?

1 : to be expected to do something They are supposed to arrive tomorrow. She was supposed to be here an hour ago. The movie was supposed to earn a lot of money at the box office, but it didn't. 2 : to be intended or expected to be something The party was supposed to be a surprise.