If you didn’t know about WhatsApp’s bold, italics, and strikethrough features, you do now.
It’s incredibly simple, you’ll need to insert a symbol either side of the text you want to make bold, italic, or with a “strikethrough.”
As per the screenshot, it’s a “*” either side for bold, “_” either side for italic, and a “~” for strikethrough (though we’re struggling to figure out what that’s useful for).