A metal roof dripping with no rain

That is condensation. Humid air inside condenses on the cold underside of the metal and drips, typically on clear cold nights. It is not a leak and sealing the roof will not help.

By timing. A leak follows rain or snowmelt. Condensation follows temperature and appears in dry weather, often spread evenly across the panel underside rather than concentrated at one point.

Only if the assembly is designed properly. Insulation without a vapour and air strategy can move the condensing surface rather than remove it. In an unheated building, ventilation and a ground vapour barrier are usually the better first steps.

A great deal. Ground moisture rising through an earth or unsealed slab floor is one of the largest humidity sources in an outbuilding, and a ground vapour barrier is often the highest-value single measure.

On new or replacement panels it is generally worth asking about. It holds condensed moisture in a felt-like layer until conditions let it re-evaporate, rather than letting it form drops and fall.

Record the weather each time water appears. Anything appearing only after rain or snowmelt is a leak; anything appearing on dry cold nights is condensation. A building can genuinely have both, and they need different work.

Shoulder-season swings, where warm humid days are followed by cold clear nights, are a common trigger, since the temperature differential driving condensation is often sharpest during those transitions. Deep winter with consistently cold conditions can produce it too, just with a different pattern.

It can reduce the humidity available to condense, particularly in a smaller or better-sealed structure, but it does not address ground moisture rising through an unsealed floor, which is often the larger source in a barn or garage.

Generally less severe over a sealed concrete floor, since an unsealed earth or dirt floor allows more ground moisture to rise into the building's air. A concrete floor still allows condensation from other humidity sources, just typically less than an open dirt floor.

Not significantly — condensation is driven by the temperature difference between the interior air's dew point and the cold panel surface, which relates to insulation, ventilation, and interior humidity rather than the roof's color or solar absorption.

Yes — dripping condensation can rust tools and equipment, damage stored materials, and create a persistently damp environment even in a building where the roof covering itself is unaffected structurally. It is worth addressing for that reason alone.

Ventilation that helps in winter generally helps year-round, since it manages moisture and temperature extremes in both directions — a well-ventilated building is less prone to summer heat buildup as well as winter condensation.