Can I use a Speedlight 430EX II on my Canon 5D Mark IV (on the camera)? I'm not looking to have it fire other flashes — just want to use it on the camera.
Yes. This is a Canon-brand flash and it will work on Canon-brand cameras. From Canon's web site for the 430 EX II:
Compatible Cameras: All Canon EOS cameras; PowerShot G series cameras
The Canon 5D is an EOS camera.
Yes, you can use any of the Canon EX speedlite units on the flash hotshoe of a Canon dSLR, and it will be compatible and won't hurt your camera. You just cannot access the 2012 features that were added with the -RT flash units, that your 5DMkIV can do.
That is, you can't use the 430EXII as a shutter remote, or use it in Gr mode as an off-camera optical slave, etc. And, obviously, it doesn't have an RT radio receiver built-in, like the 430EX III-RT.
But it can be controlled via the camera's flash control menu (the 430EX Mk I cannot), and will properly fire, perform eTTL, 2nd curtain, and HSS (high-speed sync).