Marriage Starts at Sex or Not - Quick & Clear Bible Study

"I live with my boyfriend already so we are already married in my opinion, we don't need a wedding to be married." Have you heard someone say this or similar? Is this right?

When does marriage start? Is it when the wedding happens? How about the first time a couple has sex, could that be considered the time their marriage starts?

Is a wedding needed for a man and woman to marry? Or is a wedding just a man-made idea where really a marriage starts when the couple first has sex and therefore a wedding is not really needed?

What is the Biblical answer? Let's take a look using the Bible.

Verses used in this study:
Genesis 2:24
Matthew 1:18-20,24,25
Hebrews 13:4
1 Corinthians 6:16
1 Corinthians 7:2,39
Proverbs 31:10
Mark 6:17-19
Leviticus 20:21
John 3:36
Mark 10:2-9