Me costó entender la metáfora al principio, pero la estrofa final y la rima del poema me ayudaron mucho.

In Spanish, costar + infinitive is a very common way to say that something was difficult for someone.

• Me costó entender... = I found it hard to understand...
• Literally, it is more like It was hard for me to understand...

Here, me is an indirect object pronoun meaning to me / for me.

Some similar examples:

• Me costó dormir. = I had trouble sleeping.
• Le costó aceptar la verdad. = It was hard for him/her to accept the truth.

So me costó entender la metáfora is a very natural Spanish structure.

Because after costó, Spanish normally uses an infinitive to express the action that was difficult.

• Me costó entender la metáfora.
• Not: Me costó entendí la metáfora.

This works like English It was hard for me to understand..., where to understand is also not fully conjugated.

More examples:

• Me costó aprender los verbos. = It was hard for me to learn the verbs.
• Nos costó encontrar la casa. = It was hard for us to find the house.

Costó is the preterite, which presents the difficulty as a completed event in the past.

• Me costó entender la metáfora... suggests a finished experience: at that time, understanding it was difficult, but the situation moved forward.

If you said me costaba, it would sound more like an ongoing or repeated difficulty:

• Me costaba entender la metáfora = I was finding / used to find the metaphor difficult to understand.

In this sentence, the speaker seems to be describing a specific past experience that was later resolved by the final stanza and the rhyme, so costó fits well.

Al is the contraction of a + el.

• a + el = al

So:

• al principio = literally at the beginning
• more naturally in English here: at first / initially

This is a fixed, very common expression.

Compare:

• Al principio no lo entendía. = At first I didn’t understand it.
• Al final lo comprendí. = In the end I understood it.

Do not say a el principio; it must contract to al principio.

Spanish uses the definite article more often than English.

Here, the articles sound natural because the speaker is referring to specific things within the poem:

• la metáfora = the metaphor
• la estrofa final = the final stanza
• la rima del poema = the rhyme of the poem

Even when English might sometimes omit an article in a broader context, Spanish often keeps it.

Also note the noun genders:

• la metáfora — feminine
• la estrofa — feminine
• la rima — feminine
• el poema — masculine

In Spanish, adjectives often come after the noun.

So:

• la estrofa final = the final stanza
• la rima perfecta = the perfect rhyme

Putting the adjective before the noun is usually less neutral and can sound literary, emphatic, or unusual depending on the adjective.

Here, la estrofa final is the normal order.

Because the subject is compound: two things are doing the helping.

The subject is:

• la estrofa final
• y la rima del poema

Together they form a plural subject, so the verb must be plural:

• la estrofa final y la rima del poema me ayudaron mucho

If there were only one subject, you would use singular:

• La estrofa final me ayudó mucho.

This me again means me / to me and shows who received the help.

• ...me ayudaron mucho = ...helped me a lot

Spanish often uses object pronouns like this directly before a conjugated verb.

Compare:

• Me ayudó el profesor. = The teacher helped me.
• Nos ayudaron los ejemplos. = The examples helped us.

So the sentence has two different verbs, and each one has its own me:

• Me costó... = it was hard for me
• ...me ayudaron... = they helped me

Del is the contraction of de + el.

• de + el = del

So:

• la rima del poema = the rhyme of the poem

Just like al, this contraction is required.

Do not say de el poema in this case.

Also, del poema most directly modifies la rima, meaning the poem’s rhyme or the rhyme in the poem.

Grammatically, del poema is attached most directly to la rima:

• la estrofa final y la rima del poema

So literally it is the final stanza and the rhyme of the poem.

However, in meaning, it is understood that both the stanza and the rhyme belong to the poem. Spanish often avoids repeating information that is already obvious.

A more explicit version would be:

• la estrofa final del poema y la rima del poema

But that sounds repetitive, so the original sentence is more natural.

Because mucho here is an adverb meaning a lot or very much, modifying the verb ayudaron.

• me ayudaron mucho = they helped me a lot

Use muy before adjectives or adverbs:

• muy difícil = very difficult
• muy bien = very well

Use mucho with verbs:

• me gustó mucho = I liked it a lot
• me ayudó mucho = it helped me a lot

So:

• muy ayudaron ❌
• ayudaron mucho ✅

Yes. The accent marks matter for both pronunciation and sometimes meaning/form.

• costó has the stress on the last syllable: cos-TÓ
• metáfora has the stress on TA: me-TÁ-fo-ra

In costó, the written accent also helps mark it as a past tense form.

Without the accent, costo would be a different word/form.

So the accents are not optional; they are part of correct spelling.

Yes, in this sentence you probably could.

• Me costó entender la metáfora...
• Me costó comprender la metáfora...

Both mean to understand, and both sound natural.

That said, entender is often slightly more common in everyday speech, while comprender can sound a bit more formal or sometimes a bit more complete/deep, depending on context.

In this sentence, either works well.