im wondering what would be the easiest way to melt plastic to form it into different things, like the type of plastic shampoo bottles are made out of.

no particular project, it was just something i was wondering how to to, like if i needed to make a custom part or something.

you can't just melt any kind of plastic.
PET plastic which is what your shampoo bottle is probably made from will just shrink and deform if you try to melt it.

depending on what kind of part you are making will decide what type of plastic you want to use and what process you want to follow.

DIY options.

PET is Vacuum formed usually at a fairly low heat compared to your idea of "melting" plastic... PET is formed by heating it untill it becomes soft (not liquid like melting suggests) and stretched into shape by air pressure. PET is used to form thin simple shaped objects without much strength.

If you want to mold something from a premade form I suggest a 2 part epoxy which can make small strong parts with high detail.

If you want to hand shape something and then file it to fit I suggest a hardening silicon putty

Commercial Options

Injection molding is probably what you are imagining but it is very expensive and wasteful. this is when a liquid plastic is forced into a mold and cooled. this is how most of your game system cases are build (with exception of dreamcasts as they were hand carved out of blocks of 100% pure awesome)

there are commercial vacuum forming systems also that require computer controlled temperatures and pressures to work properly.

I absolutely love machining small parts out of plastic and have many custom parts for nerf guns, rc cars and aircraft.

Don

thanks that helped a lot (not trying to be sarcastic)

It will take more than sarcasm to stop me giving bad advice.

sorry,but is ther a cheaper option than silicone putty its kinda expensive?