Pallas Just for clarity: she says I should not use the metronome when I'm practicing playing through anything.
I don’t use metronome when practicing pieces. Never felt the need to, either. That is not to say tempo creep does not happen. Or after a fermata, I can be back precisely to the original tempo. To check those, I listen to playback while clapping my hands.
When I practice scales, cadence, and arpeggios, my metronome stays on the whole time. For those exercises, even tempo is crucial, and I need to keep it in check in realtime, not afterwards.