Learn Portuguese (Portugal): Daqui a dez anos, a metrópole terá mudado muito. - Ten years from now, the metropolis will have changed a lot.

terá mudado is the Futuro Composto (Future Perfect). It is used because the sentence looks forward to a specific point in the future (Daqui a dez anos) and describes an action that will already be completed by that time. If you used mudará, it would just mean the city will undergo changes, without emphasizing that the transformation will be finished by that ten-year mark.

The lesson mentions using haver as an auxiliary verb. Could I say haverá mudado instead of terá mudado?

Yes, you can. haverá mudado is grammatically correct and means the exact same thing. However, in modern Portuguese, using ter as the auxiliary verb for compound tenses is much more common and natural in everyday speech than using haver.

How exactly does the phrase Daqui a dez anos translate to 'Ten years from now'?

Daqui is a contraction of de + aqui (literally 'from here'). When you follow it with the preposition a and a duration of time, like dez anos, the phrase literally translates to 'from here to ten years'. This is the standard Portuguese formula for saying that an event will happen a certain amount of time from the present.

Why does metrópole require an accent mark?

metrópole is stressed on the third-to-last syllable (me-TRÓ-po-le). In Portuguese, any word with this stress pattern (known as an esdrúxula word) must always have a written accent mark to show that the stress does not fall on the second-to-last syllable, which is the default rule for words ending in vowels.