Learn Spanish (Latin America): Este metal sí que parece cobre.

The phrase sí que is used for emphatic affirmation, often when there is a counter-expectation. While Este metal parece cobre just means 'This metal looks like copper', adding sí que translates more like 'This metal sure looks like copper' or 'really does look like copper'. It implies the speaker is surprised by the resemblance, or confirming it after someone else previously doubted it.

Could I just use realmente instead of sí que?

You could use realmente (really), but sí que is much more common in everyday spoken Spanish for this kind of conversational emphasis. It carries a strong 'I told you so' or 'wow, it actually does' vibe that a standard adverb like realmente doesn't capture quite as well.

Why is it parece cobre and not se parece a cobre?

We use parecer (without se) when followed by an adjective or a noun acting as a general description, like the material cobre. If you were comparing two specific, distinct entities (like two specific objects), you would use parecerse a, as in Este metal se parece a ese metal. Because copper is a broad substance category here, the simple parece is the natural choice.

Why isn't there an article before cobre, like parece el cobre?