MODAL VERBS

Have to / need to / be able to

They can use any verbal tense - "We will have to call him tomorrow"

They use negative particles - "She doesn't need to bring a coat"

Do not mistake or mix them

RIGHT "She needs to bring a coat", "She need bring a coat"

WRONG: "She needn't to bring a coat" "She doesn't need bring a coat"

They refer to a past situation

The meaning of the modal does not change

Structure: S + modal + have + participle (have never changes)

"I could have brought my camera, but I didn't want to lose it"

"They must have forgotten something, they are never late"