"Metal contraption" refers to a device or object made primarily of metal materials. It implies that it is a complex or mechanical structure. Full definition
After our meal was devoured, out came this darling little metal contraption with strawberries, blackberries and little puffs of meringue popped onto the points of the arms with a bowl of powered sugar to dip the lovelies into! (notesongs.com)
That meant that there were long periods of time each day when there was nobody in the store, and all that delicious sugary goodness was just sitting in this big metal contraption, undisturbed. (businessinsider.com)
Car seat design has come a long way since the flimsy metal contraptions of the 1930s. (bestcarseathub.com)