The smallest division on a metric ruler depends on the ruler itself. Here's a breakdown:

* Most Common: The most common smallest division is 1 millimeter (mm). This is usually marked with a short line.

* Larger Rulers: Some rulers might have smaller divisions like:

* 0.5 millimeters (0.5 mm)

* 0.1 millimeters (0.1 mm)

* Specialized Rulers: There are specialized rulers with even finer divisions for very precise measurements.

Important Note: Always check the markings on your specific ruler to determine the smallest division it has.