Both the steel and aluminium markets have faced enormous influxes of cheap Chinese metals in recent years - to the extent that in recent months those Chinese imports have actually been cheaper than the cost of production in Europe.
But while it's worth being aware of these dynamics, which are pushing cheap steel into many markets, it's also worth noting that the US actually imports far less from China than you might have thought.
So if aluminium and steel are going up in price then that means, all else equal, that the cost of making everything from aircraft wings to steel rivets also goes up.
But nothing comes for free, and even if Donald Trump's tariffs succeed in persuading domestic producers to smelt more aluminium or steel, such things don't happen overnight.
According to the US Geological Survey, America's "net import reliance ratio" for aluminium is close to 50%, implying it is deeply dependent on imports to satisfy demand among its companies.
