Yo meto la botella en la mochila antes de salir.

I put the bottle in the backpack before leaving.

Breakdown of Yo meto la botella en la mochila antes de salir.

• yo: I
• en: in
• antes de: before
• salir: to leave

Questions & Answers about Yo meto la botella en la mochila antes de salir.

Is meter the best verb here? Could I use poner, guardar, or echar?

All work, but with nuances:

• meter: to put something inside an enclosed space. Best match here.
• poner: general “to put/place.” Poner la botella en la mochila is fine, but less specific about “inside.”
• guardar: to put away/store for later. Guardo la botella en la mochila = I put it away in my backpack.
• echar: in many places, “to throw/put in” informally. Echa la botella en la mochila sounds casual/regional.

Do I need the subject pronoun Yo? Should I drop it?

You can drop it. Meto la botella… is perfectly natural. Keep Yo for emphasis or contrast (e.g., Yo meto la botella…, not someone else).

Should it be en la mochila or en mi mochila?

If it’s your backpack, you’d usually say en mi mochila. En la mochila suggests a specific backpack already known in context (e.g., the one we’re talking about). Without context, mi mochila feels more natural.

Why la botella and not una botella?

• la botella = a specific, identifiable bottle (the one we both know about).
• una botella = any bottle, non-specific.
  Use una if you mean “a bottle” in general.