MUST/CAN′T/MAY/MIGHT/COULD: (CEFR Level - INTERMEDIATE - B1+)
USE: We use MUST when we are sure about something. We use CAN′T when we are sure that something is not true or possible. We use MAY, MIGHT or COULD when we think that something is possible.
EXAMPLES: He must be at home now. The lights are on. It can′t be far. We have been driving for hours. She is still not here, so she might be stuck in a traffic jam. He is almost 2 metres tall. He might be a basketball player. It could be Lucy at the door. She said she would come round.