Se o sabor da sopa estiver estranho, eu vou comer outra coisa.

Se means if. It introduces a condition:

• Se o sabor da sopa estiver estranho = If the soup tastes strange / if the flavor of the soup is strange
• eu vou comer outra coisa = I’m going to eat something else

So the whole sentence is a normal if + result structure.

Because after se referring to a future possibility, Portuguese normally uses the future subjunctive.

So:

• Se ... estiver ... = If ... is / turns out to be ...
• not Se ... está ... when talking about a future possibility

In this sentence, the speaker is not describing the soup’s flavor right now as a fact. They mean something like:

• If the soup turns out to taste strange, I’ll eat something else.

That is why estiver is the natural choice.

It comes from estar.

Here it is in the future subjunctive:

• se eu estiver
• se você/ele/ela estiver
• se nós estivermos
• se vocês/eles/elas estiverem

So o sabor da sopa estiver estranho means the flavor of the soup is strange / turns out strange under that future condition.

Because estranho agrees with sabor, not with sopa.

• o sabor = masculine singular
• therefore estranho = masculine singular

Even though sopa is feminine, it is inside da sopa and is not the word being described by estranho.

So the structure is:

• o sabor → main noun
• da sopa → of the soup
• estranho describes sabor

Da is a contraction of de + a:

• de = of
• a = the (feminine singular)
• de + a = da

So:

• o sabor da sopa = the flavor of the soup

This kind of contraction is extremely common in Portuguese.

Using o sabor da sopa focuses specifically on the taste/flavor, not on the soup in general.

Compare:

• Se o sabor da sopa estiver estranho... = if the taste is strange
• Se a sopa estiver estranha... = if the soup itself seems strange

Both can work, but the original sentence is more precise because it points directly to the flavor.

Both can mean a future action, but vou comer is much more common in everyday Brazilian Portuguese.

• eu vou comer outra coisa = natural, conversational
• eu comerei outra coisa = correct, but more formal or literary

So in normal spoken Brazilian Portuguese, ir + infinitive is often preferred.

Not strictly. Portuguese often omits subject pronouns when the verb already makes the subject clear.

So both are possible:

• eu vou comer outra coisa
• vou comer outra coisa

Adding eu can give a little more emphasis or clarity, but it is not required.

Outra coisa means something else or another thing.

Portuguese often uses outro/outra without an article in expressions like this:

• outra coisa = something else
• outro dia = another day
• outra vez = another time / again

So vou comer outra coisa is a very natural way to say I’m going to eat something else.

In this sentence, estranho most naturally means something like:

• odd
• unusual
• off
• not right

When talking about food, it often suggests that the taste seems wrong, unexpected, or suspicious.

So it is not just strange in an abstract sense; it can strongly imply this doesn’t taste right.

Yes. That is completely natural and keeps the same basic meaning.

Portuguese can place the if-clause first or second:

• Se o sabor da sopa estiver estranho, eu vou comer outra coisa.
• Eu vou comer outra coisa se o sabor da sopa estiver estranho.

The first version puts more focus on the condition. The second starts with the main action.

Yes, it is natural and correct.

A Brazilian speaker might also say slightly different versions depending on style, for example:

• Se a sopa estiver estranha, vou comer outra coisa.
• Se o gosto da sopa estiver estranho, vou comer outra coisa.

But the original sentence sounds perfectly normal, especially if you want to emphasize the flavor specifically.