Modal Verbs en Inglés: Guía de Uso, Reglas y Ejemplos Prácticos

Modal Verbs

¿Cuáles son? The verbs must, can, could, may, might, will, would, shall, should and ought (to) are modal verbs.

¿Qué expresan? They express obligation, necessity, duty, advice, prohibition, lack of necessity, ability, permission, offers, suggestions, requests, logical assumptions, possibility and criticism.

Reglas

• Do not take an -s, -ing or -ed.
• Are followed by an infinitive without "to", except for ought, which is followed by a to-infinitive.
• Go before the subject in questions and are followed by not in negations.
• Do not usually have tenses. They refer to the present or future.

Must

Obligación, necesidad y deber

Must (it is your duty to do something / you are obliged to do something): You must always wear a seatbelt when in a car. (obligación)

Prohibición

Mustn't / can't (it is forbidden to do something / you are not allowed to do something / it is against the rules or the law): You mustn't / can't speak during the exam.

Consejo fuerte

Must (I strongly advise you to do something): You have a fever. You must see a doctor. (advertencia fuerte)

Tiempos de Must

Must only has present tenses. We use have to for all the other tenses:

• Present simple: must / have to
• Past simple: had to (She had to leave for Chicago yesterday.)
• Present perfect: have / has had to
• Future simple: must / will have to

Must vs. Have to

Must (it is necessary to do something): We use must when the speaker decides that something is necessary. I'm too tired. I must take a break. (Tomar decisiones por uno mismo.)

Have to (it is necessary to do something): We use have to when somebody other than the speaker has made the decision. I have to wear a uniform at work. (Que otra persona tome la decisión.) Questions and negations with have to are formed with do, does and did: She doesn't have to leave so early.

Mustn't, needn't y don't have to

• Mustn't (prohibición): You mustn't speak loudly in a library.
• Needn't (falta de necesidad, it isn't necessary to do something): You needn't pay in cash. You can pay by credit card. Instead of needn't, we can also use don't / doesn't need to or don't / doesn't have to.

Can, Could, May y Might

• Can (habilidad en el presente): She can swim very fast.
• Could (habilidad en el pasado): We use could to express general ability in the past. I could run much faster when I was younger.
• Could / May / Might (pedir permiso de forma formal): Could / Can / Might I have a look at this document?
• Can (informal) / May (más formal): We use can and may to give permission. You may sit down. You can sit down.
• Can't / mustn't / may not (para prohibir cosas): I'm afraid you can't move now. (Pero no tan exigente.)
• Can (para ayudar).

Shall, Should y Ought to

• Shall (sugerencias o preguntar opinión): What shall we do later on? We use these structures when we suggest something.
• Can / Could / Will / Would you? (pedir que alguien haga algo por nosotros): Can / Could / Will / Would you help me with my essay?
• Should / Ought to (decir que deberías hacer algo): You should / ought to wear your helmet when you ride your bike.

Habilidad en el pasado

• Was / were able to (managed to do): We use these to express what someone managed to do in a particular situation in the past. They were able to climb to the top of the mountain.
• Could (acciones repetidas en el pasado): He could sing very well at the age of ten. I couldn't ride a bike when I was two.

Asumir lógicamente algo

Must (suposiciones lógicas positivas): It must be winter. Can't (suposiciones lógicas negativas): It can't be summer.

The Passive Voice

We form the passive with the verb to be and the past participle of the main verb.

Cuándo usarla

• Cuando el agente es desconocido, no importante o obvio por el contexto: Many cars are made in Asian countries. (No sabemos o no es importante quién las fabrica.) The criminal was arrested (by the police, it is obvious).
• Cuando la acción es más importante que quien la realiza, como en titulares de noticias, artículos y procesos: Discarded material was transformed into a masterpiece.
• Para evitar asumir responsabilidad o al referirnos a un evento desagradable sin decir quién o qué tiene la culpa: Harry's glasses were broken. Does anyone know anything about it?
• Para enfatizar el agente: The tour in the gallery was given by the artist himself.
• Para hacer las afirmaciones más formales o corteses: Smoking is prohibited in the museum.

Tiempos que admiten voz pasiva

Present simple, present continuous, past simple, past continuous, future simple, present perfect, past perfect, modals e infinitive.

Reglas

• El agente no se omite cuando es una persona específica o importante, o cuando es esencial para el significado de la oración.
• Los pronombres objeto (me, you, him, etc.) se convierten en pronombres sujeto (I, you, he, etc.) en la voz pasiva.
• Usamos by + agente para decir quién o qué realiza la acción. Usamos with + instrumento / material / ingrediente para decir qué utilizó el agente para realizar la acción.
• Cuando el verbo de la oración activa va seguido de una preposición, la preposición se mantiene en la oración pasiva.

The Infinitive

Tiempos del infinitivo

The infinitive has four tenses in the active and two in the passive.

Passive

• Present infinitive: (to) be + past participle. She hopes to be given a promotion soon.
• Perfect infinitive: (to) have been + past participle. She said to have been invited to his party.