Keeping it limited to metals you have a lot of options.
You can create unlimited energy by transmuting metals from an oxidized state to a non-oxidized state. This is assuming that oxidized metals still count as metal. In principle you create an unlimited battery by breaking one part of the redox cycle.
Another useful application of transmutation is that you could pick the best state for your metal during production and once done transmute it. So you could construct buildings with aluminum, nice light weight and easily malleable. Once your building or floor is done transmute all the aluminum to steel making it strong. Note that there is carbon in steel so I am not sure if this is allowed.
Also during processing you could do very interesting things. Chips and printed circut boards (PCBs) are made of very thin layers of metal, copper and silicon. Using gold instead of copper is very nice for PCBs, so here your transmutation to gold comes in if you want. Now it's mainly used for high end application (smart phones, etc.) due to the price. But even more interesting is creating the thin layers. It would be possible to use mercury to create very thin layers or even tracks and then transmute them to gold or copper.
Basically all your metals can be used as a liquid. You could do very cheap injection molding with metals, like now is done with most plastics.
Also depending on what you would classify as a metal you can create everything from sand. Silicon is a metalloid and sand is mostly silicon oxide, so no more mining of anything, just use sand for everything. You could build a sandcastle and make a solid steel house of it.
As a minor side note you would also have saved the universe from an energy death.