Methanol is highly soluble in water, therefore, large amounts of methanol can be dissolved in water. This high solubility is caused by the short hydrocarbon chain and the presence of a hydroxyl group.
Alcohols all consist of one hydroxyl group attached to a hydrocarbon chain. The hydroxyl group is hydrophilic and forms hydrogen bonds with the water molecules, allowing the alcohol to dissolve in water. The hydrocarbon chain is hydrophobic and forms bonds with other hydrocarbon chains. The hydrogen bond between the hydroxyl group and water is stronger than the bonds between hydrocarbon chains if the chains are very short. The hydrocarbon chain of methanol contains only one carbon, allowing water molecules to bond freely with the hydroxyl groups.