Ahh, the metric system. Usually students either have an easy time with this or they think it's the most confusing thing, ever.
My students this year, however, did fairly well with the metric conversions. I think a large part of this success is because we spent so much time in the beginning of the year building number sense and working with powers of ten.
I also modeled exactly what a meter looks like and passed around a meter stick:
As with every math unit, we did a gallery walk with challenge questions before the test:
We also did some sorting activities and used our "I have, who has" cards in small groups.
I also sent them on a scavenger hunt in their own fridges to find items that were listed in the customary system but that were also labeled with the metric system.
How do you teach the metric system?