The Bass Guitar In Modern Music

[Curious]

Hello,
I was just wondering if someone could give me an expanded explanation of the importance of the bass guitar. I understand the basic premise that it creates the foundation on which the guitarists build their music, but I don't understand anything really more than this (other than it also provides a music deeper sound for the song).

Also, many modern songs in hard rock and metal genres often seem to have bass lines (I mean the sound created by the bass guitar, if that makes sense) that are very hard to hear. Even some bands that play more moderate or pop rock often have a bass guitarist but they bass line that he/she is creating seems to hard to distinguish over the noise of the other instruments.

I have seen lots of bass solo movies in which I can fully hear and appreciate the sound of the bass (they were mainly funk style solos) but I often have difficulty hearing them in many bands. So I am also wondering if it is just me having problems hearing them or if many bands have very quiet bass lines.

Thanks