Using "would" with "if"

Question

I read from several books and grammar websites that we don't use "would/will/shall" in "If clause".

But I was looking up the meaning of a word in Cambridge dictionary and I got stunned to see there "would" used even in "If clause".

The sentence is here:

"If you would move sideways to the left, I can get everyone in the picture."

In the above sentence the modal future "would" has been used in the "If clause" either.

I'd like to know: why is the word "would" used in that if-clause, although the grammar books say not to do so.

Answer 1

There are some exceptions to the rule of not using modals in “if clauses”.

Here I refer specifically to your question:

if you will / would = if you wouldn't mind...See source

This exception to the rule doesn't have a conditional meaning. This helps to explain why they are exceptions. Here we are using if + will or if + would as polite requests with the same meaning as if you wouldn't mind:

Answer 2

• Will you please close the door.

This "will" is not the auxiliary for future tense. Here "will" has its original sense expressing volition. And sometimes you can find "would " in an if-clause, then this "would" does not denote Conditional mode, but is used as the past form of "will" as in the example above.

It is almost impossible to explain in English the difference between German wollen/ich will/ich wollte and würde. I can only try to explain

• "If you would move sideways" has the the sense of "If you had the kindness to move sideways".

But I see that does not make things clear. The meaning of wollte and würde is so intermingled in English "would" that is impossible to separate these meanings.