Advice On Essay Structure

The fact of the matter is that there is no single best essay structure. As long as you tick the boxes for the band criteria and the essay makes sense, you'll get the marks. However, the key word in the question is "Compare" and if you write the first half about poem A and the second half about poem B, comparing them is going to be very difficult because you're going to be wanting to make constant comparisons. I would always write a paragraph about a technique used in poem A, then say how poem B uses this technique or uses a different technique to achieve a similar affect and continue in that manner, summing up the comparisons in the conclusion. You absolutely do not want to put your comparisons in the conclusion. You want to make all of your comparisons in the main body. The conclusion is exactly what it sounds like: you conclude the comparisons and statements you've already made.

What would be the best way to structure the introduction?

Like should I explain what each poem discusses?