Need, dare, and used to are considered "semi-modal verbs" because they function in much the same way as modal verbs - they are an auxiliary verb that adds information to the main verb, but can't really function alone.
They are different from modal verbs, though, because they behave more like typical verbs - for example, they change to agree with their subjects, they change tense, and they can be combined with other helping verbs like be, have, and do.
Need is used...
Dare is used...
Used to is used...
"Ought to" -- both a modal verb and a semi-modal verb
"Ought to" is a bit of a special case. It has a lot of tendencies of modal verbs - it doesn't ever change forms or use another helping verb.
But, it looks more like a regular verb because you have to include "to" before the main verb.
It just goes to show you, there are always exceptions to the rules!
You can see elements here of both modal and semi-modal verbs. Like a modal verb, you don't add an -s to ought, even though she is in the third person singular. Like a semi-modal verb, you follow ought with to.
Again, you can see elements here of both modal and semi-modal verbs. Like a modal verb, you don't add will before ought, even though we are discussing the future. Like a semi-modal verb, you follow ought with to.