Should Christians go to parties? What does the Bible say about partying?

The short answer to this question is "it depends on the party."
Parties are popular because they are fun opportunities to get together
with friends, meet new people, and to relax and enjoy one another's
company. As human beings, we are designed to be social creatures. We
live in groups, work in groups, and socialize in groups. So when we
desire to party, we are responding to the need for human interaction,
fun, and relaxation. This is normal and natural.

For Christians, the desire for human interaction has the added
dimension of wanting and needing fellowship. The Greek word translated
"fellowship" in the New Testament is koinonia, which means
"partnership, participation, social interaction, and communication."
The important concept for Christian fellowship is "partnership." The
Bible tells us we have been called into fellowship (partnership) with
Christ (1 Corinthians 1:9), with the Father (1 John 1:3), and with the
Holy Spirit (Philippians 2:1). John tells us that, as believers, we
have fellowship with one another by virtue of the blood Jesus shed for
us on the cross (1 John 1:7). Paul adds the idea that to fellowship
with Christ is to partake of His suffering (Philippians 3:10). We are
also warned that we are not to have fellowship with evil (1
Corinthians 10:20). Just as light and darkness are incompatible, so
there should be no fellowship between Christians and sin.

The problem with the question "should Christians go to parties?" is
that the "parties" being asked about are almost always not "fellowship
parties." There is no reason to even ask the question regarding
parties that are focused on Christian fellowship. No, this question is
almost always in regards to parties that involve alcohol, drugs,
and/or sex. Certainly, there are non-Christians who can party
innocently, but a party that involves things that are immoral and/or
illegal must be avoided. As believers, we are to guard ourselves
against temptation, remembering that "bad company corrupts good
character" (1 Corinthians 15:33). Further, attending parties where
sinful activities occur—even if we don't participate in them—weakens
our witness and brings reproach on the name of Christ (Romans
2:24)."Everyone who confesses the name of the Lord must turn away from
wickedness" (2 Timothy 2:19).

There are those who might see going to parties as an opportunity to
share Christ with unbelievers, and while we are to be ready with an
answer for the hope within us at all times, that presupposes
unbelievers at a party are interested in the gospel. Rarely does such
an opportunity arise at a party where drinking, drug use, and sexual
activity are occurring. Therefore, while Christians should take every
opportunity to fellowship with other believers, we must be discerning
about opening ourselves up to temptation or anything that would
compromise our life in Christ and our witness to a watching world.