Description of the problem or steps to reproduce
Pass a directory to micro as the first argument, it will complain that you tried to open a directory.
Maybe this is just me, but my preferred behaviour would be for micro to use that directory as its working directory, and just open a blank file. So that I could then open files from that directory using Ctrl+O, or using the Filemanager plugin.
My workflow in Sublime and Atom is to open the project directory I'm going to be working in, and then open the files I want from the sidebar. Micro's filemanager plugin makes that almost possible, except that I have to change directory first and then open micro.