木材 and 金属: material categories and parts
Distinguish timber from metal and read different materials assigned to different parts.
Wood as a material
木材, read もくざい, means timber or wood used as material. 木材を運びました。 means transporting timber.
木材で棚を作りました。 means making a shelf from wood. Distinguish this from planting a tree.
The metal category
金属, read きんぞく, means metal. この部品は金属でできています。 says that this component is made of metal.
金属の種類は分かりません。 says that the type of metal is unknown. Do not arbitrarily identify it as iron or copper.
Several materials in one object
板は木材で、脚は金属です。 says that the board is wood and the legs are metal. Different parts of one object may have different materials.
木材だけで作ったわけではありません。 says that it was not made solely of wood. It does not mean that no wood was used.
What are the legs made of in 板は木材で、脚は金属です?
Show the answer and why
Metal, distinct from the wood used for the board.