Some Spanish modal verbs
I recently was asked what are the modal verbs in Spanish. For those interested, some of them are:
poder = can / to be able to
deber = must
querer = to want to
soler = to used to... / I normally...
10 Answers
Hecho en Mex asked.
What does a "modal" verb mean?
The problem is that all the teaching books refer to Modals as "auxiliary verbs".
The main auxiliary verbs in English are:
to do
to be
to have
These are also normal verbs which have past / present / future tenses and "aspects" such as Simple - Perfect - Continous - Perfect continuous.
Modals have none of these qualities and therefore in my opinion should not be called "auxiliary verbs"
The 11 Modals are
can - could
will - would
shall - should
used to - ought to
may - might
must.
If I make a simple sentence such as:
"I eat a lot."
I can put any of the 11 Modals before "eat" to make 11 new sentences. Which is a really powerful characteristic of the English language.
Example: I can eat a lot - I could eat a lot - I will eat a lot - I would eat a lot etc.
I can also change the pronoun "I" for any other ones without modifying anything else in the sentence.
Example:
He can eat a lot - We can eat a lot etc.
I hope this helps you.
To the English ear to use to and to be used to says different things.
So does it to a Spanish one. "Estar acostumbrado a algo" and "soler hacer algo" are, in my humble opinion, totally different concepts.
I usually + verb = Suelo + infinitivo
I used to + verb = Solía + infinitivo
I'm used to ...= Estoy acostumbrada a ...
This is where I have to "butt" in - these may be verbs that can be used as one would use "to have to" or "to need" in English.
The "but" is that the 2 I quote above are not Modals but regular verbs - as are the those quoted by Lazarus.
Those quoted by lazarus are of course the Spanish verbs most used to derive the Spanish when writing English sentences that contain Modals.
That does not make them the equivalent of English Modals.
And here comes the question: What exactly is a modal verb in Spanish?
Querer is but desear is not?
Acabo de leer un texto muy interesante al respecto en el que de hecho el verbo querer no se incluye como modal . De hecho comparan el comportamiento del verbo querer que admite complemento directo a un verbo modal puro como puede ser el verbo deber.
Este texto es muy interesante . Pero no sé después de todo si muy fiable, ya que está escrito por un americano, me supongo por su nombre.
Modals have none of these qualities and therefore in my opinion should not be called "auxiliary verbs"
While I understand the reasoning behind this statement, I would point out that verbs which demonstrate an incomplete conjugation (such as has been described of the English modal auxiliaries) are generally categorized as "defective verbs" yet verbs, nonetheless. Aside from English, defective verbs occur in many languages including Spanish, French, Dutch, Latin and Arabic.
One argument for the terminology of "modal auxiliary verb" is that these words perform exactly the function specified by such a title (i.e. they exhibit exactly those qualities which define an auxiliary verb). That is, auxiliary verbs are those which accompany the main verb and provide further information (semantic or syntactic) or alter slightly its function to make distinctions in mood, voice, aspect or tense. In the case of modal auxiliary verbs, the distinction made is in regards to mood (as indicated by the word "modal").
to be use to
We know that he knows the difference in meaning for an English speaker since he mentioned in the other thread about soler.
To the English ear to use to and to be used to says different things.
I used to [to use to] lie, cheat, steal, and profane, but since then I have seen the light.
I am used to [to be use to] checking to see if a member is new to the site.
I think the 2nd acostumbrado meaning is closer to Spanish soler.
When we use to use to we often imply that we do not still do it.
But that is all off topic concerning modals.
A few more listed here:

I know I'm late to the party but have been reading most of the comments on this thread thinking about soler.
I learned that 'soler' was more closely related to 'always'. For example, "Los domingos solía ir al parque para caminar," which I would translate as "On Sundays I always went to the park to walk" or, perhaps more accurately, "I would always go to the park to walk on Sundays"
For me, 'accustomed to" and 'used to' have different connotations, but I'm curious if I am using it incorrectly, or if it just has wider use.
What does a "modal" verb mean?