I can only tell you about how we do it here in the Netherlands, but very rarely.

We have highway location markers (in the form of a little pole and a sign with some markings on them) every hundred meters. Their official name is “afstandspaal” but people generally call them “hectometerpaal” because they denote the distance along a highway in hectometers.

When you hear about traffic jams, speed cameras, or car accidents on the radio, they’ll usually announce highway number and hectometer pole number so drivers know where to look.

The metric tonne (1000kg) is used rather than a megagram even though megagram is more fun to say. This is for historic reasons, mostly. Having Mg (megagrams) and mg (milligrams) next to each other would probably also just confuse people.

Hectares (100x100m, or 10000m²) are used to denote area for things like farms. Centiliters and deciliters are used for very specific purposes (medical and such).

As for general distance: meters and kilometers work fine. Same with grams and kilograms. Smaller measurements like centimeters and millimeters are also common (or milliliters and liters, rarely centiliters but you do see them in some recipes).

Funnily enough, we (although I notice it mostly among older people) do use ons and pond (ounce and pound), although an ons is 100 grams and a pond is 500 grams. Just like with the tonne, we adjusted them to make dealing with SI units easier; we did the same with the mijl (mile) and other units similar to the imperial name as a transition to the normal metric system. Technically speaking, you’re not allowed to sell advertise products by the ons or pond anymore (thanks, IJkwet of 1937) but if you ask anyone at market for a pound if cheese, they’ll know how much to get you.

Lastly, there are a few use cases where the inch is used. Screens are measured in inches for reasons I’m not entirely sure about (probably British and American exports). This leads to some rather silly phone spec sheets, listing width/length/height in centimeters and a screen diagonal in inches. We don’t even use a Dutch word for inch!