Learn Italian: La musica è il mio hobby.

In Italian, you generally need to use a definite article (like la or il) when talking about broad categories, concepts, or abstract nouns. So while we just say "Music" in English, Italian requires "The music" (La musica).

Why is there an il before mio? Doesn't mio already mean "my"?

Yes, mio means "my", but Italian almost always pairs a possessive word with a definite article. You are literally saying "the my hobby" (il mio hobby). A major exception to this rule is for singular family members (like mio fratello), but for things like hobbies, you must include the article.

The word hobby comes from English. Does it still have a gender in Italian?

Yes! Most foreign words borrowed into Italian automatically become masculine. That's why it is paired with the masculine words il and mio.

This lesson is about expressing preferences. How would I change this sentence to say "I like music"?

You would say Mi piace la musica (literally: "The music is pleasing to me"). Notice that you use the singular piace because la musica is a singular noun, rather than mi piacciono which you use for plural nouns.