In order to understand iambic pentameter one must understand the first rule of poetic structure: structure affects content. Understanding the poem's content requires understanding the poem's structure.
Once you understand the basics of iambic pentameter, you can more accurately analyze the author's purpose and discover literary gold. A look at The Prologue to Romeo and Juliet, for example, shows that the opening sonnet has two important breaks from the standard iamb that affect one's understanding of the play (you'll have to click on the analysis of The Prologue to Romeo and Juliet and scroll down to number three to get an explanation (the other example is in line 1 of the prologue, first word, I'll let you figure out the why).
Whether your'e a student or a teacher, Brighthub has what you need to better understand iambic pentameter.