charles3xxx
Modal verbs what are they?
4 Answers
These are verbs that are usually used in conjunction with a following verb in the infinitive.
EX. Deseo/quiero desayunar ahora. I want to have breakfast now.
Los estudiantes deben estudiar para el examen. The students should study for the exam.
Here is a chart with the most common ones.

You need to understand Modals to speak English fluently.
The 11 Modals are often called "Auxiliary verbs" but in my opinion they are not verbs because they cannot be conjugated. They have the same form for all "persons" he - she - you - we - they - it.
Modals never change form but they modify the meaning of the verb that follows the Modal.
He can speak Spanish. He could speak Spanish. - possibility or ability
He will speak Spanish. He would speak Spanish. - future
He shall speak Spanish. He should speak Spanish. - future and obligatiuon
He may speak Spanish. He might speak Spanish. - permission and possibility
He used to speak Spanish. He ought to speak Spanish.- past and obligation
He must speak Spanish. - obligation
All the sentences above are good sentences.
(Él) puede hablar español. Podía hablar español.
Hablará español. Hablaba español.
Hablará español. Debe hablar español.
Puede hablar español. Podría hablar español.
Solía hablar español. Debe hablar español.
Debe hablar español.
These sentences might not be good or not the only possibilities.
Estas frases pueden no ser buenas o no son las únicas posibilidades. All Modals are followed by the infinitive of a verb without the "to".
Dani's answer is good. but "want" is not a Modal.
PS - the English Modals do not exist as direct word for word in Spanish.
Modals do not have past forms or future forms.
It is not possible for example to say " I will can do it tomorrow ".
The reason is that two Modals, for example will and can, can never be used next to each other.
Therefore no modals can be made future by using them with will.
These Modals can be used with the present perfect of a verb to indicate the past.
could I could have done it. (but I didn't)
may I may have eaten it. (but I can't remember)
might I might have written it. (but I'm not sure)
should I should have asked for it. (but unfortunately I didn't)
would I would have prevented it. (but I did not have enough time/money/opportunity)
ought to I ought to have helped her. (but I forgot)
must I must have cooked it. (No one else could have done it)