Question for Programmers and the Like

Say that there are pieces of metal and no computers exist. How would a processor be built, how would it be worked (manual switches?), and how would it give an output?

First computers -> vacuum tubes, from there you move to basic transistors and just keep getting smaller and smaller. Currently, Intel is down to 32nm transitors and is currently working on 22nm. As for output, vacuum tubes function almost exactly like transistors do. This is one reason why they were so easily replaced by them.

Oh and as a side question, how does an infinite loop destroy the pieces of metal that make up the processor, or cause them to malfunction (in terms of physical processes) so that they are forever destroyed or unusable?

First, an infinite loop doesn't destroy your CPU, anyone that's accidently made a coding error or torture tested their CPU/GPU can attest to that. Second, metal is not the biggest component of computer hardware. When hardware breaks down, it's generally the transistors (namely Metal-Oxide-Semiconductor Field-Effect Transistors - MOSFETs) which, outside the contacts, are not metal at all (Silicon and silicon dioxide being the most common pairing, though SiO2 is being replaced by high K dialectrics in new processors). Now, as for how they are destroyed, errrrrr, that's complicated. Basically, too much heat or voltage can cause the transistor to deteriorate over time. However, even under use, CPUs are made to last at least 10 years by which point most people buy new computers.

My apologies if this isn't conherent in any way, shape, or form...