There is a 'metric' coordinate system, it's called EPSG:3857 and uses meters as its units. Although it is not valid close to the poles and can give error of up

There is a 'metric' coordinate system, it's called EPSG:3857 and uses meters as its units. Although it is not valid close to the poles and can give error of up to 0.6% so it's not useful for when you need high accuracy or to cover the entire globe. Most places in world also have local coordinate systems that reproject smaller geographic areas to cartesian coordinates with meter units for making easier to work in those areas.