The lock screen is what you see when your phone is locked. It's really divided into two parts, one when the screen is off - where "always-on display" can give you some information, or the proper lock screen where the screen is fully on, but you can't access the the device.
Turn on always on display: To have the screen show you "always on" information, head into lock screen and security > always on display and switch it on. This shows when the phone display is in standby, i.e. when the display is otherwise off. If you want it to always show, scroll down and toggle that option on. If you want it on a schedule - perhaps only show when you're at your desk - then turn off "show always" and set a schedule instead. This will also let you turn always-on display on or off a night depending on your preference.
Change always-on display layout: You can customise what you see in always-on display by heading to the section above. You can opt to show the home button or not as well a the clock or information.
Change the always-on clock style: There are a range of different clock types for he S9 always-on display. Head into settings > lock screen and security > clock and facewidgets > clock style. Here you can change the clock both for always-on display and the lock screen. You can also chnge the colours, so if you don't want mono, you can select something else. Add a music controller to your lock screen or always-on display: Facewidgets are the name Samsung uses for other information on your lock screen or always-on display. You'll likely have a music controller there by default, but if you don't, head into settings > lock screen and security > clock and facewidgets > facewidgets. Here you'll find a range of options for the always-on display, so you can change tracks, for example, without unlocking your phone. You'll have to double tap on the always-on display to switch to the music controller, however.
Change the brightness of the always-on display: This is linked to auto brightness on your phone, however you can manually over-ride this to set the brightness yourself. Head into settings > lock screen and security > always-on display. Within this menu you'll see "auto brightness". Turn this off and you can set the brightness yourself. Top tip: If auto brightness is off, you can double tap on the always-on clock and a brightness scale will pop-up.
