This guide was designed to work with both the Metro and the Metro Express. The main way to tell if your board is the express is if it says "express" on the board. There's also a SWD port on the bottom of the Metro Express which isn't present on the Metro. The diagram below points these two differences out:
This guide will work without any modification, follow the regular steps and have fun!
There are two things to look out for while you work through this guide:
1) Wiring: Some circuits have an extra wiring page called "Wiring for Metro Express" and some don't. If the circuit you are looking at does not have this sub-page, use the regular Metro wiring. If you see the Metro Express Wiring page, use the wiring in that page instead.
2) Code: If there needs to be a modification in code for Metro Express, instructions will be present to switch the code to a Metro Express compatible code.