Learn Spanish (Latin America): Me gusta esta canción porque ella canta perfectamente. - I like this song because she sings perfectly.

To make an adverb ending in -mente (which is like "-ly" in English), you start with the feminine form of the adjective. The adjective for "perfect" is perfecto, so we use the feminine perfecta and add -mente, giving us perfectamente.

Why is it esta canción and not este canción?

Nouns that end in -ción, like canción, are almost always feminine in Spanish. Because it is feminine and singular, we use the feminine word for "this", which is esta.

Why do we use Me gusta instead of a "yo" form for "I like"?

The verb gustar actually means "to be pleasing to". So Me gusta esta canción literally translates to "This song is pleasing to me". The song is the subject doing the action, which is why we use the "it" form of the verb (gusta).

Why doesn't porque have an accent mark or a space here?

When written as one word without an accent (porque), it means "because". If it were written as two words with an accent (por qué), it would mean "why", which is used in questions.