How do I change to the metric system on my watch?

Which watch do you have?

Vívoactive 4

From the manual - vívoactive 4/4S - Changing the Units of Measure

Changing the Units of Measure

You can customize units of measure for distance, pace and speed, elevation, weight, height, and temperature.

1. Hold Back button (lower/right button)
2. Select Settings > System > Units.
3. Select a measurement type.
4. Select a unit of measure.

Thank you so much