Exactly how Google produces its results is a closely guarded secret, at least regarding what information factors in the ranking algorithms. Conversely, they have openly announced something they don't pay any attention to: meta keywords. What does this mean to you? Well, if you spend time cramming keywords into your meta tags in the hope that you'll climb the rankings, then waste no more time because it's official.
Hear it directly from the mouth of Senior Google engineer, Matt Cutts.
"But I thought keywords mattered?", you say. Yes, they do. But only within your page content. You see, Google search is pretty clever - it knows that if someone types a keyword phrase into their search engine, they want to find a page that specifically relates to their search phrase. Keyword phrases that are contained within page headings, link text and URLs are given the most weight, and the text within your page will then act to complement these elements with efficient use of keyword phrases.
Matt Cutts makes the important point that the meta description data is considered by Google's algorithm, and that this should be used effectively for best results. For details on how to add a custom meta description to you page or post, see my article Optimise your page with All in One SEO pack.
See more related articles on the SEO fundamentals page.