Q:how do you attach wood to metal?
Today, there are many types of silicon glues that can join these two materials together, but the most secure solution, especially if you are going exterior, is screws.
It’s an example for a facade. In my case (from left to right) there are wood panels, but the principle is the same for metal. The screws go instead in metal bolts, they are screwed in wooden cube (replacing the bolts). Do you get me?