Start in Web Connect and set your display profile to metric. Also, check your device settings in web connect. That should do it as web Connect typically overwrites other settings. However you can also check Mobile Connect and the Approach's settings if that isn't enough.
Thanks pshare, I just found the settings as trickky for me. When we select the unit as "Meter", S20 asks cm(height) and kg(weight) automatically. And if we seklect "Yard", then S20 asks lbs(weight) and feet(height). Anyway I solved my issue. Surprising application beyond intuitive....