Antes de salir, mete la fiambrera y el termo en la mochila, que luego tenemos hambre.

Mete is the affirmative tú command of meter.

• meter = to put / to place / to stick in
• mete = put!

So the sentence is giving an instruction to one person in an informal way:

• Mete la fiambrera y el termo en la mochila = Put the lunchbox and the thermos in the backpack.

If it were negative, Spanish would use a different form:

• No metas la fiambrera... = Don’t put the lunchbox...

After antes de, Spanish normally uses an infinitive when the subject is the same as the main clause or when the subject is understood in a general way.

• Antes de salir = before leaving / before you leave

This is very common:

• Antes de comer = before eating
• Después de trabajar = after working

If Spanish needs to make the subject explicit or different, it often uses:

• antes de que + subjunctive

For example:

• Antes de que salgas = before you leave

So antes de salir is completely natural here.

In Spain, fiambrera usually means a lunchbox, food container, or something like a Tupperware-style container used to carry food.

Depending on context, it could be:

• a lunchbox for school or work
• a plastic container with prepared food inside

It is a very Spain-specific everyday word. In other Spanish-speaking countries, people may prefer other words.

Termo means a thermos, vacuum flask, or insulated container for keeping drinks hot or cold.

In this sentence, it is most likely:

• a thermos flask with a drink inside

So:

• la fiambrera y el termo = the lunchbox and the thermos

Spanish uses the definite article much more often than English.

Here, the speaker is referring to specific, known items:

• la fiambrera = the lunchbox
• el termo = the thermos
• la mochila = the backpack

In English, you might sometimes leave out an article or use a possessive, like your backpack, but Spanish often just uses the when the context makes it clear whose thing it is.

So Spanish naturally says:

• en la mochila

where English might say:

• in the backpack
• or in your backpack

The verb meter is commonly used with en to mean put something into something.

Pattern:

• meter + object + en + place/container

Examples:

• Mete las llaves en el bolso. = Put the keys in the bag.
• Mete la ropa en la maleta. = Put the clothes in the suitcase.

So:

• Mete la fiambrera y el termo en la mochila = Put the lunchbox and the thermos into the backpack.

This is a very natural everyday structure.

Here, que introduces an explanation or reason. In natural English, it works a bit like:

• because
• since
• as

So the sentence means something like:

• Put the lunchbox and the thermos in the backpack, because we’ll be hungry later.

This use of que is very common in spoken Spanish, especially in casual reminders, instructions, or justifications.

Examples:

• Abrígate, que hace frío. = Put a coat on, because it’s cold.
• Date prisa, que llegamos tarde. = Hurry up, because we’re late.

So this que is not that here. It is a conversational way to give a reason.

In Spanish, the normal way to say to be hungry is:

• tener hambre = literally, to have hunger

So:

• tenemos hambre = we are hungry

This is the standard everyday expression.

You can say estar hambriento/a, but that sounds:

• more descriptive
• sometimes more emphatic
• sometimes a bit less neutral in everyday conversation

So in ordinary speech, tener hambre is the most natural choice.

Not necessarily. Spanish often uses the present tense to talk about the near future or something understood from context.

So:

• luego tenemos hambre literally looks like later we are hungry
• but naturally means we’ll be hungry later

The word luego already signals that this is about the future, so the present tense sounds perfectly normal.

Spanish could also say:

• que luego tendremos hambre

but tenemos is very common and natural in speech.

Tenemos means we have, so it refers to the speaker plus at least one other person.

In this sentence, the speaker is telling one person:

• mete = you, put it in

But the reason involves a group:

• tenemos hambre = we’ll be hungry

So the idea is something like:

• You put the food in the backpack, because later we will be hungry.

That we probably includes the speaker and the listener, and maybe other people too.

Yes, the commas help show the structure of the sentence.

• Antes de salir, sets off the introductory time phrase: Before leaving
• ..., que luego tenemos hambre. separates the main command from the explanatory comment

So the punctuation reflects natural pauses:

• Antes de salir, / mete la fiambrera y el termo en la mochila, / que luego tenemos hambre.

In writing, this makes the sentence clearer and more natural.