To use figures of speech such as metaphors -- comparisons of two things that don't use like or as -- it definitely helps to have examples. The trick with using metaphors is to watch out for cliches and avoid mixing them. Expressions like "the calm before the storm," "Mother Nature," or "he's a rat," have been used so often that they're now cliches. Although it's difficult to avoid cliches altogether, make an effort to either use more original metaphors, or simply choose straightforward description.
Another common problem with regard to metaphors is the tendency to mix them or overwork them, usually from careless thinking, as in the example above, or over thinking.