Los verbos modales o “auxiliares modales” son : WILL, SHALL, CAN, COULD, MAY, MIGHT, MUST, OUGHT TO, WOULD y SHOULD

1. Will/Shall:

Además de utilizarse para el futuro simple, WILL se usa…

• para señalar una promesa : My friend said that he will give me a ride home this evening.
• para un pedido urgente : Will you answer the phone for me, please?SHALL se utiliza…
• para hacer una sugerencia u ofrecimiento como pregunta:
  Shall we buy tickets for the concert? – sugerencia
  Shall I help Derek with the presentation? – ofrecimiento 2. Can/Could :

  Can y Could se usan…

• para describir habilidad o voluntad de hacer algo en el presente o pasado:
  Jill can speak Spanish very well. – habilidad
  I can make tea if you wish. – voluntad
  My brother could play golf twenty years ago – habilidad pasada
  Steve could take photographs until he lost his camera – voluntad pasada  
• también para dar una explicación o pedir permiso:
  You can freeze bread for a month. – explicación
  Can I use your telephone please? – permiso  
• para expresar percepción delante de los verbos : feel, hear, see
  I can see a boat on the river.
  Keanu could hear the doorbell despite the music.
  We can feel the sun across the window.  
• para explicar una posibilidad y hacer una sugerencia en presente y futuro (could)
  Your old guitar could be in the attic – presente
  We could go to the movies next weekend – futuro
  Could you help me? – presente 3. May/Might :

   

• para expresar una posibilidad o hacer una sugerencia en presente o futuro.
  If you come tomorrow, you may see Sam.
  If you return tomorrow, you might see Sam. Might indica menos certeza que may.

   

• para pedir o dar permiso (may)
  The nurse may leave at 5 if she finishes her work. – dar permiso
  May I call you tonight? – pedir permiso 4. Must :

   

• para explicar obligación o gran necesidad cuando no existen otras opciones. (must con Presente Simple y Futuros)
  You must wear a uniform at that school – obligación
  We must have a pet! – necesidad  
• para señalar un hecho en presente (must)
  para señalar un hecho en pasado (must have)
  He must like Mary. They go out every night.
  The street is wet, it must have rained during the night. 5. Ought to:

   

• para expresar obligación y dar consejo
  We ought to send an answer to the offer today.
  Johnny ought to leave now to get to school early . Ought to tiene el mismo significado que should.

  6. Would :

   

• para describir o hablar sobre una situación o actividad imaginada.
  I would like to travel around the world.
  Einstein would know the answer to that problem.  
• para pedir información o solicitar algo
  Would you send me the data?
   
• para hacer o aceptar una invitación
  Would you like to go to the movies with us?
  I would love to go.  
• para reportar estilo indirecto, informar sobre eventos, actividades, situaciones, hechos en pasado, expresados primero con “will” en estilo directo
  original : She said, ” I will go with you.”
  indirecto: She said that she would go with you.  
• para ofrecer un consejo o alguna cosa en general
  If I were you, I would study more.
  Would you like a soda or a beer? 7. Should :

   

• para expresar obligación o gran necesidad, con la alternativa de no hacerlo.
  Teachers should stay until 5PM. (deberían pero pueden no hacerlo)  
• para expresar opiniones en forma de consejos.
  I think your brother should change his job.
  You should tell us your ideas. Should tiene el mismo significado que ought to