Wrath as an attribute of God
Because God is perfect and without any spot or blemish (without the effects of or nature of sin), and because He is the only completely sovereign Being in existence, He has the right to take on a righteous anger or wrath against those that commit sin against himself. Often times this attribute is misunderstood to mean that God is some sort of tyrant that goes around looking for victims of His wrath, without justification. However, this could not be further from the way the God of the Bible is portrayed. Sure, there are passages in the Bible that could look very terrible, but often times they are prefixed with God giving them many opportunities to repent and turn back to Himself. Usually the only part that is ever heard about though is the part that sounds the most gruesome, which is simply the righteous judgment of God being carried out on a people that would not turn to Him.
Wrath of God against sin stands in contrast to the Grace of God available for all who repent and turn from their sin.