What about a rubber band, can it change its shape? Is it a solid?

Yes it is a solid

Explanation:

It just has unusual properties.

Does it float when you drop it? then it is not a gas.

Does it pour into any container as water does? Then it is not a liquid.

So it's a solid.

And it can change it's shape

Yes, it is.

Explanation: Rubber band is ab elastic material which when stretched changes it's original shape.