Rattling at idle, clutch not depressed

Something is rattling at idle, I recently had my clutch replaced but that did not stop the rattling. When I depress the clutch the rattling stops.
There is also a chunky metal noise when decelerating in low gears.
After I drive it for a bit the rattling becomes significantly louder, at idle, but when I depress the clutch, it stops and cannot be heard at all. Could it be the clutch release bearing? Or something else? I should note that the rattling cannot be heard once the car is moving.