Most missionaries lead small, infomral, evnagelistic Bible studies. The leader may need to create the study straight from scripture and personal research.It's hard work but it's incredibly rewarding.
Since many who come aren't believers and know nothing about the Bible, they have hard quesitons. They may dump their life problems out onto the table. They want real answers and real help. If God's Word is the foundation for life, studying the Bible is absolutely necessary to changed lives. The study leader won't have all the answers but God will use His Word to heal and restore the most broken people.
Bible studies are the building block for new churches. When people come to faith in Christ and study scripture, they want to gather with others who also believe. Bible studies grow into congregations, and a church is born. As believers are mentored, they too can start Bible studies that reach out to others who are curious, hurting, and looking for answers.