In this article, we will discuss metaboxes and metafields in WordPress. Specifically, we’ll cover how to replace the old PHP metaboxes in Gutenberg and extend Gutenberg’s sidebar to add a React component that will be used to manipulate the metadata using the global JavaScript Redux-like stores. Note that metadata in Gutenberg can also be manipulated using blocks. And both ways are discussed in my course, however, in this article I am going to focus on managing metadata in the sidebar since I believe this method will be used more often.