Pasuk (21:9):

"And Moshe made a serpent of copper and placed it on a pole, and it was that anyone who was bitten and looked at it, lived."

The people started to complain, due to the fact that they thought that they were traveling away from Eretz Yisroel, and they were afraid that they would not have anything to eat and drink, and thus die in the desert.  They were punished for their needless complaints, for there was a miraculous well which followed them and they had the Manna to eat.  They started to complain about the Manna, that it was a spiritual food, and that it would not sustain them for the heavy agricultural work which they would have to do in the future.

Hashem sent fiery serpents as a form of punishment, these serpents would bring a deathly illness to those who were bitten.  The people begged Moshe to pray to Hashem to accept their repentance and to remove the serpents.  Hashem told Moshe to place a serpent on a pole, and whoever would look at it will be healed from their bite.

Moshe made the serpent out of copper, even though Hashem never told Moshe to make it out of copper.  What brought Moshe to make the snake out of copper?

Rashi explains that Hashem told him to make a snake (Nachash) and copper (Nechoshes) comes from the same root.
Was this just a play on words, or is their something deeper which we can learn from this?
Rav David Feinstein answers that Moshe saw that a fiery snake can kill by just spitting out its venom, and slander & gossip can fool people into thinking that they are allowed to speak that way about another person,  while really their venomous words can cause great harm to others.
The Bnei Yisroel sinned by spreading gossip about Hashem (and the Manna).  They fooled themselves into thinking that what they were saying was proper.

Moshe saw the similarity between the magic of the snake, and the magic of Lashon Hara, and he tried to fight this with a third magic, copper.
Copper has the ability to fool people into thinking that it is gold.  It wasn't just a play on words.

And it was:
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If we take a closer look at the Pasuk, we would see that the Torah uses the word of "Vehaya", and "it was that if a snake bit a person...".  We also know from the Midrash that the term "Vehaya" denotes joy.  What is the connection of joy to a person being bitten by a venomous snake?

The Meshech Chachma explains that we learn from the previous Pasuk that, anyone who was ill and looked at the brass snake on the pole, would live.  Even if someone was ill previously from a deathly illness, he would be healed.  This is the joy which one would feel from the snake bite, for now he would be completely healed from his prior deathly illness.
Rabbi Pliskin explains that even though this joy was only felt by a minority of the people, the other people were able to empathize with those who were sick, for they were able to see a positive outcome of their suffering.  They felt happiness for others who gained from the suffering.  Also, at times one who suffers gains afterwards.  It is just hard to see this during ones hard times.


Why do we pray?
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Rabbi C.Y. Goldwicht ZT"L explains that we usually think that one prays because we always have troubles and we are always lacking things, thus we pray to Hashem to fill this lacking.  We may think that our goal in prayer is to fill our requests.  Prayer is used to reach our goals.  

This is not true.  Our Rabbis teach us that a person was created in this world lacking, and through sincere prayer, one can receive from Hashem.  Hashem wants to hear the prayers of the righteous.  For this is the connection between man and his creator.  The lack is only there to be used as a tool to require one to pray and thus increase the connection to ones creator.  The main goal for our lacking, is to increase our connection with Hashem, through prayer.

This was the reason why the Maan fell every day and not once a year or once a month, for they had to feel a lacking each day, and this brought out prayer, which connected the Bnei Yisroel to their creator.

Hashem used the snake as a punishment, for this was the best form of punishment.  A snake has its food readily available to it, for it was cursed to eat sand all its life.  This is a curse?  Food readily available?

This is the actual curse, for the snake is totally disconnected from its creator.  The fact that it crawls on the ground in dirt, is a sign of disgust from the creator. (Due to its sin with Chava)

The final redemption from our long exile will happen before its time, only if we show a true wanting, through our prayers.  Let us bring this connection through prayer, and bring the world closer to what it was created for.


 
(Adapted from Artscroll Chumash, Kol Dodi, Growth through Torah, Asufat MaArachot)