If it's not possible I would like to learn how to ... so people from google (or from whatever search engine) can reach my articles.
We bloggers cannot access metadata and insert keywords however, that matters little given that these days search engines are focused on keywords in your content and not in your tags. http://onecoolsitebloggingtips.com/2012/03/01/revisiting-keywords-and-tags/
These 5 videos introduce how Google discovers, crawls, indexes your site’s pages, and how Google displays them in search results. It also touches lightly upon challenges webmasters and search engines face, such as duplicate content http://onecoolsitebloggingtips.com/2010/03/22/5google-webmasters-video-tutorials/
If you are using a WordPress.com theme good SEO is a given. However, going beyond the theme what the blogger has done within that structure is worth evaluating. Whether you write informative, persuasive or controversial content learning how search engines work, and how to apply basic SEO to you content will benefit your blog as it will increase traffic from targeted readers. http://onecoolsitebloggingtips.com/2011/10/21/two-seo-videos-for-bloggers/