Bolt that comes through top of wheel well

Hi, I have a 2000 Chevy Blazer 4x4 and noticed my
tires were leaking from the rim on drivers side. Well
first let me say I'm a female who's dad got on me to
always inspect my vehicle. So as I was doing so I
noticed on the wheel well at the very top there is a
bolt. I live in Michigan so you know with snow
comes salt. It looks like the salt started erroding
away the price that the bolt comes through and it
staring to pull through. Can someone please tell
me what this bolt is for. Unfortunately I lost my dad  
on Christmas so I have nobody to ask. I can and do
fix just things myself but don't know where to start.
Again it's the drivers side front wheel well at the
very top. Thank you so much in advance. It makes
me a little nervous driving with it now seeing that
bolt. I don't know if it's just a body bolt or if it goes
to the tranny. Again thank you