alright, in a solid, the particles are tightly packed together in an orderly manner and they only vibrate about in fixed positions. in order to overcome the forces of attraction, heat must be applied. example you want to melt iron to molten state, you must heat it up until the forces of attraction in between the particles weaken so that they'll become so called molten *liquid(?)*. in the molten state the particles are still packed closely together but not a tightly as in solid and they have no regular arrangement and the particles slide past one another.
I hope this helps sorry that it's long
