Els guants negres són els que porto quan vaig en bicicleta al matí.

The two els do different jobs:

• Els guants negres = the black gloves
  Here els is the definite article, masculine plural.

• són els que porto = are the ones that I wear
  Here els means the ones.

So the structure is:

• Els guants negres = the black gloves
• són els que porto = are the ones I wear

This is very natural in Catalan.

Els que means the ones that or those that.

In this sentence:

• els que porto = the ones that I wear

It is a very common pattern in Catalan:

• el que = the one that / what
• la que = the one that
• els que = the ones that
• les que = the ones that

The form changes to match gender and number.

Catalan, like Spanish, often distinguishes between ser and estar.

Here són is from ser, because the sentence is identifying which gloves they are:

• Els guants negres són els que porto...
  = The black gloves are the ones I wear...

This is identification, not a temporary state or location, so ser is the natural choice.

There is one: it is built into els que.

• els que porto = the ones that I wear

The que is the relative word here, introducing the clause porto.

Catalan often uses que where English uses that, which, or sometimes nothing at all.

Yes, portar can mean to carry, but it also very commonly means to wear.

So:

• porto uns guants = I am wearing gloves / I wear gloves
• porto una jaqueta = I’m wearing a jacket

This is completely normal Catalan usage.

Because the sentence describes a habitual action:

• els que porto quan vaig en bicicleta al matí
  = the ones I wear when I go cycling in the morning

The present tense is often used in Catalan for regular or repeated actions, just like in English:

• I wear
• I go

So porto and vaig both describe something the speaker normally does.

Because this sentence refers to a real, habitual situation.

• quan vaig en bicicleta al matí = when I go cycling in the morning

With quan, Catalan often uses the present indicative for habitual or factual actions.

If the sentence were about an uncertain future situation, Catalan might use a different structure, sometimes with the subjunctive. But here it is just a routine fact, so vaig is correct.

Vaig en bicicleta literally means I go by bicycle or I go on a bicycle.

In Catalan, anar en bicicleta is the standard expression for to go by bike / to ride a bike.

So:

• vaig en bicicleta = I go by bike / I ride a bike

The preposition en is the normal one in this expression.

Usually en bicicleta is the normal and preferred expression.

• anar en bicicleta = to go by bike

Using amb bicicleta would sound less standard in this context. Amb means with, so it does not express the usual idea of means of transport as naturally here.

For a learner, it is best to remember:

• en cotxe
• en tren
• en autobús
• en bicicleta

Catalan often uses the article with parts of the day.

• al matí = in the morning
• a la tarda = in the afternoon
• a la nit = at night / in the evening

Here al is a contraction of a + el:

• a + el matí → al matí

This is one of those patterns that English speakers often need to get used to, because English usually says just in the morning without a separate article in the same way.

Because in Catalan, adjectives often come after the noun.

So:

• guants negres = black gloves
• cotxe vermell = red car
• casa gran = big house

This is the normal order for many descriptive adjectives in Catalan.

Because it agrees with guants, which is masculine plural.

• guant = glove
• guants = gloves

So the adjective must also be masculine plural:

• negre = black, masculine singular
• negres = black, plural

Agreement is very important in Catalan: articles, nouns, and adjectives often have to match in gender and number.

Catalan often leaves out subject pronouns because the verb ending already shows the person.

• porto already means I wear
• vaig already means I go

So jo is not necessary unless you want emphasis or contrast.

For example:

• Jo porto els negres, no els blaus.
  = I wear the black ones, not the blue ones.

But in a neutral sentence, leaving out jo is completely normal.

Yes. Catalan often uses els que to avoid repeating the noun.

Instead of saying something like:

• Els guants negres són els guants que porto...

it is much more natural to say:

• Els guants negres són els que porto...

This works like English the ones that..., which also avoids repetition.

You would change the article, noun, adjective, and verb agreement as needed.

For example:

• El guant negre és el que porto quan vaig en bicicleta al matí.

Changes:

• Els → El
• guants → guant
• negres → negre
• són → és
• els que → el que

This shows how strongly Catalan marks number and agreement.