Modals: must, have to

Learn how to use must and have to

“Must” and “have to” are modal verbs to express certainty, a requirement or obligation.

Must:

It is used to express a strong or definite requirement. It’s stronger than “Have to”. You can use it in different ways. Must is usually translated into Spanish as “deber”

Look at these examples:

• To express certainty:

This must be the correct address, look at the sign. Esta debe ser la dirección correcta, mira el cartel.
They are not at home, they must be on vacation. No están en casa, deben estar de vacaciones.
He must be lost on his first day in Hong Kong. Debe estar perdido en su primer día en Hong Kong.
I’m sorry, it must be hard for you. Lo siento, debe ser duro para ti.

• To express obligation

I must submit my report by Friday. Debo entregar mi informe antes del viernes.
You must wear a mask when entering the building. Debe llevar mascarilla al entrar en el edificio.
She must attend all the classes in order to pass the course. Debe asistir a todas las clases para aprobar el curso.
You must renew your driver’s license before it expires. Debe renovar su carné de conducir antes de que caduque.

• To express prohibition (negative form)

You must not smoke in this area. No debe fumar en esta zona.
He must not copy other people’s work. No debe copiar el trabajo de otras personas.
They must not use their phones during class. No deben utilizar el teléfono durante la clase.
We must not exceed the speed limit on this road. No debemos superar el límite de velocidad en esta carretera.

Have to

It is used to express certainty as well and requirements but it’s softer than must. Have to is usually translated into Spanish as “tener que”

See these examples:

• To express certainty:

The kids are quiet, they have to be planning something. Los niños están callados, tienen que estar planeando algo.
Is this the embassy? It has to be, it’s the only building with a flag. ¿Es esta la embajada? Tiene que ser, es el único edificio con bandera.
This has to be true, everyone knows it. Esto tiene que ser verdad, todo el mundo lo sabe.
This has to be milk, it’s white. Esto tiene que ser leche, es blanco.

• To express necessity:

I have to buy groceries before the store closes. Tengo que comprar comida antes de que cierre la tienda.
We have to be careful to be quiet. Tenemos que tener cuidado de no hacer ruido.
I have to study for my exam tonight. Tengo que estudiar para mi examen de esta noche.
You have to remember to bring your ID to the meeting. Tienes que acordarte de llevar tu carné a la reunión.

• To express obligation:

He has to take his medicine at the same time every day. Tiene que tomar la medicación todos los días a la misma hora.
I have to call my parents every Sunday. Tengo que llamar a mis padres todos los domingos.
We have to finish this project by the end of the week. Tenemos que terminar este proyecto antes de que acabe la semana.
They have to have the right tools for the job. Tienen que tener las herramientas adecuadas para el trabajo.

👉 Note:
Don’t have to and must not are different:

• Must not=prohibition. You must not smoke here.
• Don’t have to= it is not necessary. We don’t have to leave now (we can if we want to, but it’s not necessary)