I think the OP's remark about metric was referring to the units used for setting the pressure sub-scale, not to the units used to measure the Altitude of the aircraft (correct me if I am wrong!).
In some parts of the world a unit called "Torrs" is used as an altimeter setting; 1 Torr is approximately 1 mm of Mercury and 760 Torrs equals exactly the Sea Level pressure in a standard atmosphere (ie 760 Torr = 1013.2Hpa = 29.92 InHg). I have used it when landing at an airport in Russia!
See here if you want to know more ...
Torr - Wikipedia, the free encyclopedia
Modern EFIS equipped transport category aircraft have an option in a menu of the EFIS to change from Hpa to InHg and back again; you change half way across the Atlantic from 1013Hpa to 29.92 InHg. There was no option to choose Torrs when in Russia so we used a conversion table on paper and set the equivalent Hpa setting.
Using Metres in place of Feet to define Altitudes, Heights or Flight Levels is of course common in many parts of the world and again, EFIS aircraft usually have an option but otherwise you just use a conversion table and set the equivalent.
Happy landings
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