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MODAL VERBS

Modals verbs are a class of auxiliary verbs. Modal verbs are also called modal auxiliaries or simply manners. There are ten English modal verbs:
Can – Could; May – Might; Shall – Should; Will - Would; Must - Ought to

Modal verbs express the mode of a verb: the ability, possibility, necessity or another condition of the main verb. In English, the main verb is always ininfinitive without to, except the modal ought. In a statement, the word order is subject + modal + main verb.
For Example:
|Principio del formulario |Modal |Main Verb |
|Subject | | |
|They|can |come |
|Mike |should |walk |

Principio del formulario
Final del formulario
In the questions, word order is subject + modal + main verb.
Yes / no questions (yes-no questions)
|Principio del formulario|Subject |Main Verb |
|Modal | | |
|Can |They |come? |
|Should |mike|drive? |

Informative questions (wh-questions)
|wh- Word |Modal |Subject |Main verb |
|When |can |They |Come? |
|How|could |he |Know? |

CHARACTERISTIC OF THESE VERBS

- S are not in the third person singular present simple
- Do or does not need to form the negative or interrogative.
- Infinitive are never behind, except Be Able to, Need to, Have to and ought to.
- They have no infinitive, participle and compoundtenses.

NOTE: The verbs have to and Need to also consider "semimodales verbs" because they meet all the characteristics of modal verbs.

CAN - COULD

The modal can, like the Spanish verb power, indicates a potential or ability.
For Example:
- Tom can help you.
- Wild animals can be dangerous.
In questions, the dog used to request permission to do something or to ask about apossibility.
For Example:
- Can I help you?
- Can Mike have dinner with us?
- Who can answer the next question?
- When can we get back the results?

Could modal indicates a possibility or ability in the past.
For example:
- I could have told you that.
- It could have been a disaster.
- When I was young, I could run very fast.

Could be used to speculate aboutfuture possibilities. In these examples, Could and Might are synonymous.
For example:
- It could / might rain tonight
- This could / might be dangerous.

In the questions yes or no, Could speculates on some potential in the present or the future.
For example:
- Could she be the murderer?
- Could this be a mistake

Could indicate an option.
For example:
- We could go seea movie.
- I could become a doctor.

In the questions yes or no, Could make a polite request. In these examples, Could and can are synonymous.
For example:
- Could / Can you open your window?
- Could / Can you help me move this sofa?

Could be used to form the conditional that contains two sentences: one with "if" (yes) and the other with the result. Could prayer is on the...