When I was first making a blog/site I wanted a static site, so I could host it on github pages without needing a backend. Octobers seemed like the best choice at the time because it was quick and easy to setup. Octopress is based on Jekyll, which is probably the most popular static website generator. It also had a number of pre-made templates which meant saving time on writing my own CSS.
The move should not be very difficult as both Octopress and Metalsmith work from a source directory and all my posts are already in a markdown format. I’ve made a couple static websites using metalsmith, and have posted a metalsmith skeleton to github for myself and others to use when starting a metalsmith site/blog.