Learn Portuguese (Portugal): Esta canção é linda.

Esta means "this" and is used to point to a specific feminine singular noun, which is canção in this sentence. You use este for masculine nouns. Isto also means "this", but it is a neutral word used for abstract ideas or unknown objects, and it is never placed directly before a noun.

Is there a trick to knowing that canção is a feminine noun?

Yes! Almost all Portuguese nouns that end in -ção are feminine. This is a very reliable rule that helps you know to use feminine words around it, like Esta and linda.

Why is the verb é used here instead of está?

We use é (from the verb ser) because the beauty of the song is considered a permanent, inherent quality. We use estar (like está) for temporary states or conditions, but a song being beautiful does not change from one moment to the next.

Could I say Esta canção é bonita instead?

Yes, you can. Both bonita (pretty) and linda (beautiful/gorgeous) work perfectly here. Linda just expresses a slightly stronger feeling of beauty than bonita.