This is the nice thing about WordPress—it's all "dynamic". Once you install WordPress and design a great theme for it, anyone with the right level of administrative capability can log into the Administration Panel and add, edit, or delete content and menu items. But generally, when people ask for "dynamic menus", what they really want are those appearing and disappearing drop-down menus which, I believe, they like because it quickly gives a site a very "busy" feel.
I must add my own disclaimer—I don't like dropdowns. Before you get on to my case, I will say it's not that they're "wrong" or "bad"; they just don't meet my own aesthetic standards and I personally find them non-user friendly. I'd prefer to see a menu system that, if subsections are required, displays them somewhere consistently on the page, either by having a vertical navigation expand to display subsections underneath, or showing additional subjections in a set location on the page if a horizontal menu is used...