• He was the son of Enoch.
• The root part of his name "muth" means "death".  The other root part of "shalach" means "to bring" or "to send forth".  ("Muth" ~ death is used 125 times in the Old Testament; and, "Shalach" ~ Judgment is used 60 times in the Old Testament. 
• Speculation has his birth at 3317 BCE. 
• He lived 969 years on Earth. 
• He had the longest life span of any person in the Bible.  The Earth's ecology prior to the Great Flood is said to be the cause of the extended lives.  Many PhD Scientist and Biblical Scholars believe through scientific evidence and also the scriptures that the Earth had a thick water canopy around the entire Earth that created a green-house effect which filtered out more cosmic radiation.  Additionally, the atmospheric pressure was as much as double of what it is now that between the green-house effect, atmospheric pressure and other factors gave all humans, animals and plants extended life spans.
• Because of the time of his birth and lifetime, he would have known Adam and Noah.  Because of him knowing Adam, it is belief that he is Saved as Adam would have witnessed to him.
• The bloodline of Jesus Christ is through him.
• The Scriptures do not tell us how or when he died other than he died and the Great Flood occurred after his death.
• Furthermore, regarding his death, the Scriptures do not tell us if the Great Flood occurred on the same day as Methuselah's death or if the Great Flood happed very soon afterwards. 
• Biblical Scholars believe that God used Methuselah as a prophet of warning to accept and fear God because a judgment was coming. Additionally, there is the belief by many Biblical Scholars that the reason Methuselah had the longest life-span in the antediluvian era was to give mankind adequate time / chances to repent.  This appears be confirmed because of the meaning of the names and lineage of Adam through Noah along with so many other examples in the Scriptures where God always is patient in extending His Grace.
• Since Methuselah lived 969 years, there was a great deal of time for many people to repent and there were probably many who did, albeit they would have died before Methuselah.  While this is conjecture, we know from the scriptures that the righteous are always removed from "God's judgments" and the only righteous left at the Great Flood's time was Noah and his Family.  As an example, regarding God removing the righteous, read about the angels removing Lot and his family from Sodom before it destruction, where the judgment could not happen until they were removed. 

Methuselah has part of the lineage of Noah, which started with Adam and Eve.

What to read next?

What is Salvation?  Is it possible to lose Salvation?  We have eternal life.  Evolution is not real.  When a Christian suffers is there benefits from it.  Rewards in heaven.  Do we Tithe?  What does the 3rd Commandment tell us?  What is Grace and Mercy?  Is there an Age of Accountability?  Is there a place of unending punishment and exile form God?