In most cases both modal and ordinary forms of need are possible. Note that modal forms of need are not normally used in American English.

Will need to

The structure will need to is used to talk about future obligation.

We will need to buy a chicken in case Karan comes.
You will need to work hard if you want to pass your exams.
You will need to talk to him.
She will need to get a degree.
He will need to improve his communication skills if he wants to get a good job.

Need + …ing

Need can be followed by an –ing form. This structure has the same meaning as need + to be + past participle.

Your car needs washing. (= Your car needs to be washed.)
That carpet needs cleaning again. (= That carpet needs to be cleaned again.)
She needs training. (= She needs to be trained.)
Your hair needs cutting. (= Your hair needs to be cut.)
Those plants need watering. (= Those plants need to be watered.)

Need not have + past participle

This structure is used to talk about unnecessary things that we did.

He need not have lost his temper. (= He lost his temper but it was totally unnecessary.)
She need not have applied again. (= She applied again but it was not necessary – a waste of time.)
We need not have waited for his approval.
I need not have cooked so much food – nobody was hungry.