The answer to your question is that wordpress.com is a multiuser blogging platform where we cannot access our metadata here. If we use relevant and appropriate keywords in our blog titles and also create effective taglines then we have done the best we can do.
Metadata is no longer used by Google. Matt Cutts has made this clear on many occasions It was too easily manipulated and too many unscrupulous webmasters used it to game the system. Remarkably no matter how many times Matt Cutts emphasizes that Google does not use it there are still those who till tell us it's required when it isn't.