I have a small raised bed against a wood fence, separated by aluminum sheeting. I am going to tear it down. I don't like the way it looks. A volunteer lilac has made it's home between the fence and the sheet metal. I don't want it there, and I have cut it back several times, but it keeps coming back because I need to dig up the root. This is a temporary situation for me. Landscaping blocks are a better idea. There really should be some space between the wood fence and dirt. The sheet metal helps protect the fence from direct contact. But there is moisture to consider. It creates a home for bugs. The bugs and moisture could adversely affect a wood fence.
There is a newly installed chain link fence down the street from me that has metal roofing attached to the bottom of it, about 2' up. It looks nice. The metal is more rugged looking than the flimsy sheet metal that I used to cover my wood fence. I think it must be an animal barrier. There is no raised bed garden.