That is why it is always important to have proper ventilation throughout the computer case and to have a good amount of fans within the case. Because without them, the components within the case can get extremely hot, leading to failure and electrical issues. If you know basic chemistry, then you know that every single element in the universe has a melting point, or a specific temperature where an element changes from a solid to a liquid. For water, that is 0 degrees Celsius and for a majority of components you find in your PC, like Silicon and Magnesium, melting points are at a much higher temperature. But, just because your PC isn’t melting when it’s hot doesn’t mean the heat is “healthy” for the computer. It can cause a component to completely fail, most likely causing the computer to shut itself off until the component goes back down to a reasonable temperature.
Nowadays, it is actually rather difficult to overheat a component because many are built to withstand a high temperature and to change how “hard” they are working when their temperature gets too high, so the temperature has a chance of going down. For example, a GPU with a core clock of 800 MHz may lower it to 600 MHz if its temperature gets up to 80 degrees Celsius. That way, the GPU is not performing as many tasks per cycle, which allows it to cool off since it is literally generating less heat. Another thing some components like GPUs or CPUs might do to cool off is increase its dedicated fan’s speed. Some components have a dedicated fan to ensure that the temperature stays within a normal range and if the heat starts to get too high, the computer shoots up the fan speed. The reason why the fan speed is not always at 100% is due to the fact that the fan also has a lifespan, and keeping the fan speed at maximum can lower the fan’s lifespan. Thermal paste is also used to connect two components together (like a GPU and a fan) so that the heat from one component can be transferred to another.
Of course, you can always install newer fans within your computer, to increase ventilation, but always make sure to do this when your computer is turned off. When a computer is on, there is obviously still electricity running through it, so messing around with the things plugged in can cause electrical shorts, which could ruin your computer. So yeah, absolutely don’t do that.