What are some alternatives?
When comparing Hexo and Metalsmith, you can also consider the following products
GatsbyJS - Blazing-fast static site generator for React
Jekyll - Jekyll is a simple, blog aware, static site generator.
Wintersmith - Flexible, minimalistic, multi-platform static site generator built on top of node.js
Nikola - Nikola is s static site generator tool written in Python.
Hugo - Hugo is a general-purpose website framework for generating static web pages.
Grav - The modern open source flat-file CMS