Antaŭ la vojaĝo mi metas vestojn en valizon kaj kontrolas mian pasporton.

Because antaŭ is a preposition, and la vojaĝo is its object. In ordinary use, nouns after prepositions do not take -n just because they follow a preposition.

So:

• antaŭ la vojaĝo = before the trip
• not antaŭ la vojaĝon

The -n ending is mainly used for:

• a direct object
• direction in certain expressions

Here, la vojaĝo is neither a direct object nor a directional expression.

Here antaŭ means before in a time sense.

It can also mean in front of in a place sense, but in this sentence it is clearly about time:

• antaŭ la vojaĝo = before the trip

So antaŭ can refer to either:

• time: before
• space: in front of

Esperanto has a definite article, la, but it has no indefinite article.

So:

• la vojaĝo = the trip
• valizon = a suitcase / suitcase, depending on context

In this sentence, la vojaĝo probably refers to a specific trip already known in context, while valizon is indefinite.

Metas is the present tense form of meti = to put.

Esperanto uses -as for the present tense:

• meti = to put
• metas = put / am putting

In a sentence like this, the present tense can describe:

• a habitual action: Before a trip, I put clothes in a suitcase...
• a vivid step-by-step action: Before the trip I put clothes in a suitcase...

If you wanted a future meaning, you could use metos:

• Antaŭ la vojaĝo mi metos... = Before the trip I will put...

Vestojn has two endings added to the base word vesto:

• vesto = a garment / item of clothing
• vestoj = clothes / garments
• vestojn = clothes, as a direct object

So:

• -j marks the plural
• -n marks the direct object

Since the clothes are the thing being put into the suitcase, vestojn is correct.

Yes. In Esperanto, vestoj is commonly used for clothes.

English treats clothes as a plural-only word, and Esperanto often does something similar by using the plural vestoj for clothing in general.

Compare:

• vesto = one item of clothing, one garment
• vestoj = clothes

So metas vestojn en valizon is a normal way to say put clothes into a suitcase.

This is a very common Esperanto point.

With en:

• en valizo = in a suitcase (location)
• en valizon = into a suitcase (movement/direction)

The -n here shows direction or change of place.

Because the clothes are being moved into the suitcase, Esperanto uses:

• metas vestojn en valizon

If the clothes were already there, you would say:

• La vestoj estas en valizo = The clothes are in a suitcase

Because adjectives in Esperanto agree with the nouns they describe in both number and case.

Base forms:

• mia pasporto = my passport

As a direct object:

• mian pasporton

Both words take -n because pasporton is the direct object of kontrolas, and mian must match pasporton.

This agreement is very regular in Esperanto.

Because it is the direct object of kontrolas.

The sentence says that I check my passport, so passport is the thing being checked. In Esperanto, the direct object takes -n.

So:

• mi kontrolas mian pasporton
• literally: I check my passport

This is the same reason vestojn also has -n.

Yes, and the meaning would be slightly different.

• meti = to put, place
• paki = to pack

So:

• mi metas vestojn en valizon = I put clothes into a suitcase
• mi pakas valizon = I pack a suitcase
• mi pakas miajn vestojn = I pack my clothes

The original sentence focuses on the physical action of putting clothes into the suitcase. Paki would focus more generally on packing.

The ending -as shows tense, but not the subject by itself. The form metas could mean:

• I put
• you put
• he/she/it puts
• we put
• they put

So Esperanto normally includes the subject pronoun:

• mi metas
• vi metas
• li metas, etc.

That is why mi is needed here.

Not completely. Esperanto word order is fairly flexible because endings show grammatical roles.

This sentence uses a very natural, neutral order:

• Antaŭ la vojaĝo mi metas vestojn en valizon kaj kontrolas mian pasporton.

You could move parts around for emphasis, for example:

• Mi antaŭ la vojaĝo metas vestojn en valizon...
• Mian pasporton mi kontrolas antaŭ la vojaĝo.

But the original version is the most straightforward and natural for ordinary use.

Vojaĝo is a general travel word and can often be translated as:

• trip
• journey
• sometimes voyage

In everyday contexts, trip is often the most natural English translation.

So antaŭ la vojaĝo usually means before the trip. The exact English word depends on context, but the Esperanto word itself is broad and normal.