Dare and Need to

Dare and Need to:

Dare and need are much more commonly used as non-modal verbs, taking -s or -es in the third person singular and having an infinitive and past and present participles.

Dare and need are not commonly used as auxiliaries nowadays, but formerly they both were. Neither is used in affirmative declarative sentences. An example in an exclamation is "How dare he!” expressing willingness in the face of fear or contrary obligation. The interrogative form "Dare he do it?" or "Need he do it?" is equivalent to the non-auxiliary form "Does he dare to do it?" or "Does he need to do it?"; need, of course, expresses the modality of necessity. In a negative context "He dare not do it" is equivalent to "He does not dare to do it", while "He need not do it" is equivalent to "He does not need to do it". In both cases it is the modal or entire verb phrase, rather than the main verb, that is being negated.

However, in the sentence "He does not dare to lose weight" or "He needs to lose weight," dare or need is not being used as an auxiliary, as (1) it takes the full infinitive "to lose" as the head of the verb phrase rather than the bare infinitive "lose" that occurs in a phrase like "I can lose weight", and (2) the verb following it is conjugated in the third person singular.

Both need and dare can be used as auxiliary verb and main verb. When used as auxiliary verb, it works just like other modal auxiliaries, such as 'can', 'may', 'will', 'shall', etc. When used as main verb, they are like any other verb, such as 'run', 'go', 'come', 'take', 'work', 'joke', etc.

Examples:

As auxiliary verb:

They needn't walk home, they can catch a bus.
How dare you disobey my orders?
Need you really take that risk?
She dare not make the first move at any cost.
I need drive to Joe's immediately.

As you have seen, dare and need don't agree with the subject or use 'to' when used as modal auxiliary. It's just like 'can' or 'may': such as, "I may drive to Joe's immediately", "Can you really take that risk?"

Used as normal verb:

I need to get the attestation before applying.
She does dare to do a lot of things.
Do you dare to compete with me in this?
Does she need any more help?

Now, it's just like any other normal verb. It agrees with the subject and does take 'to'.

Correct use of Dare and Need:

NEED

Only negative and interrogative sentences.

1. You need not go with him.
2. Need we write a letter?

Use of ‘need’ as a verb:
1. We shall need some money next week.
2. Do you need his services any more?

DARE

Only negative and interrogative sentences.

1. He dare not oppose me.
2. Dare she swim across this river?

Use of ‘dare’ as a verb:
1. They didn't dare to enter the room.
2. He won’t dare to oppose me.