I used Elf's Liner Sealer to turn my Müse's electric blue eyeshadow into a liner and paired it with a bronze smokey eye.
For monolids, it's important to keep your eyes open while applying your liner to make sure it's on the right spot. Don't worry if you end up with a "floating" eyeliner. This is how my eyes look with my eyes closed. You can fill up the gap later.
|The floating eyeliner.|