MODAL VERBS are auxiliary verbs used with other main verbs -the verb to be, or regular or irregular verbs- the are a help in the sentence. They show the «mood» of the next verb (muestran el humor o tono del verbo que le sigue): MODAL + infinitive (be/regular/irregular verb). Using one or other modal verb will change the tone of the communication, so we can be very direct and rude or very kind and polite depending on the modal verb we decide to use.
SOME MODAL VERBS
CAN: (puedo) ability, possibility, availability (habilidad, posibilidad, disponibilidad)
COULD: past of can (pude) or imaginary of can (podría)
SHOULD: advice or estimation (debería: consejo o estimación)
MAY/MIGHT: possibility, probability (capaz, tal vez: posibilidad, probabilidad)
WILL: future (haré)
WOULD: +ía (haría)
Grammar structure example:
AFF: I can help you
NEG: I can’t help you (la negación siempre lleva un auxiliar antes del not)
INT: Can you help me? (la pregunta siempre inicia con un auxiliar)
Tone change examples: (hacer solicitudes – pedir ayuda)

REQUESTS (solicitudes)
WOULD you MIND HELPING me? (formal)
COULD you HELP me? (polite)
CAN you HELP me? (direct)
OFFERING (ofrecer)
WOULD you LIKE something to drink?
WOULD you LIKE to come with me?
ACCEPTING (aceptar)
I WOULD LIKE to participe
I WOULD LOVE to go with you
I’D LOVE to! = me encantaría
I’D LIKE that! = me gustaría eso
ASKING FOR PERMISSION (pedir permiso)
«May I…?» = Me permite..?

MAY I ask you a question? (formal and polite)
COULD I ask you a question? (polite)
CAN I ask you a question? (informal)
SHOULD: advice or estimation (consejo o estimación)
ADVICE:
I think you should see a doctor.
You should study harder for the exam.
You shouldn’t be here now.
Should I stay or should I go?
ESTIMATION:
I believe they should be here by 6pm
We should get there any time soon.