Le métro est bloqué à cause d'un accident.

In French, you almost always need an article (like le, la, les, un, une) in front of nouns.

• Le métro literally means the subway / the metro.
• Here, le is a definite article (like the in English).

French usually doesn’t drop the article the way English sometimes does (e.g. “Subway closed” on a sign). In French, a normal sentence would say Le métro est bloqué, not just Métro est bloqué.

The accent on é (an acute accent) changes both the pronunciation and sometimes the meaning.

• é is pronounced like the ay in say.
• So métro sounds roughly like MAY-tro, not MEH-tro.

Without the accent (metro), it would be misspelled in standard French. The official spelling is métro, short for métropolitain.

The form bloqué / bloquée agrees in gender and number with the noun:

• métro is masculine singular → le métro est bloqué
• If it were feminine singular, you’d write bloquée:
  • La route est bloquée. (the road is blocked)

So:

• Masculine singular: bloqué
• Feminine singular: bloquée
• Masculine plural: bloqués
• Feminine plural: bloquées

In practice it works like an adjective describing the state of the metro: the metro is blocked.

Grammatically:

• est = present of être (to be)
• bloqué = past participle used as an adjective

You can see it’s behaving like an adjective because it agrees with the noun (bloqué / bloquée / bloqués / bloquées).

So the structure is similar to English is blocked, but French tends to treat this more like is in a blocked state.

All three can appear with transport, but they don’t mean exactly the same:

• est bloqué
  The metro cannot move because something is blocking or interrupting it (accident, congestion, obstruction, strike, etc.). Emphasis on being unable to move.

• est en panne
  The metro is broken down / out of order. Emphasis on a technical failure.

• est arrêté
  The metro is stopped. This can be neutral (just stopped at a station, at a red signal) or due to a problem. It doesn’t automatically imply a disruption.

In the sentence with à cause d’un accident, est bloqué fits well: an accident is blocking traffic.

Both express cause, but they work differently and have different structures:

• à cause de + noun

  • à cause d’un accident = because of an accident / due to an accident
  • Structure: preposition + noun
  • Often used for negative reasons or problems.

• parce que + clause

  • parce qu’il y a un accident = because there is an accident
  • Structure: conjunction + full sentence

So you could say:

• Le métro est bloqué à cause d’un accident.
• Le métro est bloqué parce qu’il y a un accident.

Both are correct; the original just chooses the à cause de + noun structure.

de becomes d’ in front of a word starting with a vowel sound. This is to make pronunciation smoother.

• de + un accident → d’un accident

So:

• à cause de la pluie (consonant sound → keep de)
• à cause d’un accident (vowel sound → d’)

It’s the same rule as in:

• de + elle → d’elle
• de + avoir → d’avoir

Because accident is grammatically masculine in French.

• Masculine: un accident
• Feminine: une
  • feminine noun (e.g. une voiture, une route)

Unfortunately, noun gender is mostly arbitrary in French. You usually have to learn each noun with its article:

• un accident
• une collision
• un problème
• une panne

You could say it, and people would understand, but it’s less natural here.

• par is used more for the agent in a passive sentence:

  • Le livre est écrit par Paul. (written by Paul)
  • Il a été renversé par une voiture. (knocked over by a car)

• à cause de is used for a cause / reason:

  • Le métro est bloqué à cause d’un accident.

So par un accident sounds a bit odd because an accident is not really an agent; it’s more a cause, which is why à cause d’un accident is preferred.

Yes. French allows you to move à cause d’un accident without changing the meaning:

• Le métro est bloqué à cause d’un accident.
• À cause d’un accident, le métro est bloqué.

Both are correct and natural. Putting the cause first simply emphasizes the accident a bit more.