The Metronome Disappears
How to play
You'll need a metronome that can mute itself on a schedule (many metronome apps have a "silent bars" mode). Set it to play four bars of click, then four bars of silence.
Play a simple groove or scale through the whole cycle. Keep the tempo steady when the click drops out.
When the click returns, listen to whether you are ahead of it, behind it or exactly with it.
Challenge
Lengthen the silence to eight bars and see where you land when the click comes back.
Tips
Tap your foot. It keeps the beat in your body when the click is gone.