Noble gases could possibly be the most 'perfect', yet least interesting elements out there. You won't see any fancy fireworks or reactions from them. In fact you might not see anything at all when you look at one - because they are nearly always gases! All the noble gases are found in the 'end group' of the periodic table (group 8), and they all share similar properties.
Noble gases are unique from any other element on the periodic table due to the fact that they are unreactive. This is because they have a 'complete' or perfect electron shell with the right number of electrons. All other types of atoms try to achieve this shell.
While other atoms desperately react to try to gain or lose electrons to perfectly complete their electron shells, noble gases don't have to worry about reacting as they already have complete electron shells.
Because they have a full shell, they hold on to their electrons very tightly. (have a high Ionisation Energy) It takes a lot of energy to take electrons away from a complete shell and only elements that had a 'high electron stealing ability' (properly called electron affinity) would be able to do this.
Whether a substance is a solid, liquid or a gas depends on how closely the different molecules in that substance are held together. In a gas, the molecules are far apart and in a solid, they are held close together. How closely in a substance molecules are held together depends on the strengths of the bonds between the different molecules.
Noble gases do not react, even with each other, so they exist as theirselves, monatomically (1 atom - i.e. Ar, instead of diatomic - i.e O2). Therefore the bonds that hold the molecules of the gas together are very weak. This is because they are bonding to the same thing - and are hardly attracted to each other due to having little normal positive and negative attractions that would occur between the molecules in most non-metals. (only have temporary dipoles/dispersion forces)
A few exceptions
Fluorine is the most reactive metal on the periodic table and has the largest electron affinity of all elements (electron stealing ability). Therefore it can react with a larger noble gas such as Xenon, which has a lower ionization energy, but only if the conditions are right.
Noble gases can also leave the gas stage at very, very low temperatures. This is because at low temperatures the molecules in the substance slow their movement and have lower energy.
The collisions between the molecules don't result in the molecules being pushed all over the place and moving away. Therefore the molecules are held closer together and will therefore change their state.
Noble gases are very unique as they are unreactive, monatomic gases which have an extremely high ionization energy (hold on to their electrons). They are different from all the other molecules that surround us.