Around 1900 aluminum was no longer more expensive than gold (Queen Victoria of England famously used aluminum plates when fine dining instead of the cheap gold ones!). The Neil Merrill company made aluminum backed parlor guitars with a wooden top 1894-1898, pretty much the same way as an Ovation guitar.
Many were sold to tropical countries like India, where the humidity melted the hide glue and made the guitar come apart or "explode" from the swelling of the wood. They made aluminum mandolins, banjos, fiddles and woodwind instruments too.
I own one of these aluminum backed guitars, and it sounds OK, but not as good as a wooden one. The tone is not metallic, but lacking in quality.
Have a look at one here.
Read some more here.