I am not really sure what may have prompted this question. Are you thinking that because there is a lot of mead drinking in the Mead Hall, that the monsters are either a figment of an alcholic stupor, or that they represent the internal "monster" of alcoholism that the warriors must overcome? If so, I can tell you that I have never heard of this interpretation with regard to Beowulf, but perhaps other teachers have and they may respond.
I cannot in my wildest dream see how the monsters could represent alcoholism. For some scholarly information about the monsters, I recommend you check out the excellent study guide right here on eNotes. You can read about what the monsters represent. This Old English epic poem describes a lot of action that goes on in the Mead Hall and drinking mead, of course, was a regular part of their comraderie. The more they drink, the bolder they sometimes get, and sometimes they wake up with hangovers, but I don't know that this is related to the monsters, which are actual beings that the men have to fight.
Yes, these three could represent alcoholism.
In fact, there are many points in the poem which suggest that they are not physical creatures.
Because I do not have the time to go into great detail, I will try and sumarize the argument in the following points:
1. The only time "Grendel" comes is when they begin drinking.
2. There is one instance in which the armed soldiers, while intoxicated, begin boasting, ending in a bloodbath at the mead-hall.
3. Only those who leave the mead-hall survive.
4. Beowulf mentions in several different points that weapons will not work against Grendel. If the creature were physical, would these not be of use? This suggests that it is an internal warfare.
5. When he "conquers" Grendel, he states that he healed the place. If it were a physical battle, would he not say that he rescued them? Perhaps, a healing of alcoholism.
6. The people continue to drink, and the conflicts with the three continue: alcoholic addiction? An endless cycle: once an addict, always an addict.
I hope that helps.