A Gandhabba also has rupa, but not such gross or dense rupa as this physical body. Lal explained on the articles that a Gandhabba always, at least, has the kammaja kaya (hadaya vatthu where the consciousness arised, as well as 5 sense-base pasada rupa). Especially if it leaves a body after death, it usually takes a small amount of matter related to the “image and form” of the deceased body with it, as far as I understand. So, it has matter and form, but that form is not visible to us with our physical eyes (while we are embodied).
A Quest to Recover Buddha's True Teachings