Modal and semi-modal verbs

Source:https://sites.google.com/site/grammarrulesmj/modals-1

• Modal verbs: https://slidetodoc.com/modal-verbs-modals-are-helping-verbs-that-do/

"What is the difference between modal and auxiliary verbs?

Auxiliary verbs add grammatical or functional meaning to the clauses in which they are used. They can be used to express aspect, voice, modality, tense, etc. For example, I have read this book so many times. “Have” is an auxiliary, which helps express the perfect aspect.

Modal verbs also fall in the category of auxiliary verbs. But they indicate the modality in a clause. You use them to express certainty, ability, willingness, necessity, permission, obligation, advice, and possibility. For instance: Mary might come tomorrow. “Might” is a modal verb here, and it shows the likelihood of a certain action. 

All modal verbs are auxiliaries, but not all auxiliaries are modal verbs.

What are the 5 main types of modals?

Depending on the meaning they express, there are five main types of modal verbs:

• Modals denoting ability: can and could. I can speak four languages. 
• Modals expressing permission: can and may. May I open the window? 
• Modals for likelihood: will, might, may, can, and could. It may rain today. 
• Modals denoting obligation: must and have to. You must do your homework regularly. 
• Modals for giving advice: should. I think you should stop smoking. 

How do you use modals correctly?

Modals may be overwhelming and difficult to remember at first, but the more you practice, the more you’re going to use them properly. There are four fundamental rules you need to bear in mind when using modals. Let's see what they are. 

• Modal verbs always come first in a verb phrase. I can swim very well.
• Modal verbs are followed by bare infinitives. You should be more careful next time. 
• You can’t add “-s”, “-ed”, or “-ing” to modals: Mary must work hard today. 
• Modal verbs form their negative and interrogative like other auxiliaries: I can't dive. "
• Source:https://www.englishcollege.com/what-difference-modals-auxiliary-5-types-use-correctly

• "Semi-Modal Verbs 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.
• The main verb that follows a semi-modal verb is always the "bare infinitive form" - the basic verb form. Remember, that with semi-modals, "to" is part of the verb phrase.
• Need communicates necessity or obligation. In formal negative constructions, need is often used without "to" before the main verb.
• Dare shows that the subject is making a conscious effort, or has great desire to do the action of the main verb. It is more often used in formal negative sentences, and more often in British English. Dare is often also used in formal questions.
• Used to conveys the idea that an action happened habitually in the past, but no longer occurs. Also, with be as a helping verb, used to gives the idea of being accustomed to doing the action of the main verb.
• "Ought to" has tendencies of both modal verbs and semi-modal verbs. Like modal verbs, it doesn't ever change forms or use another helping verb. But, like a regular verb, you have to include "to" before the main verb."

Source:https://www.turtlediary.com/lesson/semi-modal-verbs.html