06 Elantra squeaking/rubbing front wheel

A grinding or rumbling noise can also be symptoms of a wheel bearing or constant velocity joint in a driveshaft. A worn wheel bearing can also cause a 'whistling' sound (as can a worn CV joint).

A grinding noise with brakes is either worn pads causing metal to metal contact on the brake disk/rotor, or the brake backing plate catching on a spinning rotor ... or a loose/missing anti squeal brake shim (they stop the pads from rattling and vibrating).

However, as you say a mechanic has looked at the brakes and can't find anything wrong .. I think I would begin to suspect a wheel bearing or constant velocity joint on the driveshaft (front wheel drive cars).

How To replace front Brake Pads. In 90% of the car manufacturers the job will be done the same way. This is F250 Ford 2006

I would suggest you check your brakes. Jack up & block the vehicle and remove the tire. Keep an eye out for any evidence of worn or rubbing parts. Look between the pads and the disk for rocks (can cause squeaks.) Also check to see if the pads are worn down to the "squeal inindicator" If none of these are the problem, then it's likely you have a bad bearing. Unless you have the correct tools, you will probably have to take it to a pro.

Disc brakes usually include a part called a wear indicator. A wear indicator is a small piece of metal attached to the brake pad that contacts the brake rotor when the pad material has been worn down to a certain level. When the wear indicator grinds against the rotor, it makes a squealing noise as you apply the brakes. This noise is a signal which tells you it's time to have your brakes examined.
In other words, noisy brakes aren't something to mess around with. If you hear that sound when you apply the brakes in your vehicle, have them checked out as soon as possible.
I hope this helps.

I just replaced the front pads on my '09 Avenger and I'm getting a squealing sound from them only when the car go's forward. It's not a grinding noise but, more of a lite metal rubbing squeak. Any ideas?

Are the front brake pads ok? Some have squeal indicators, it is a tin plate that touches the disc (without damaging) to warn you that the brakes are worn. On the initial stages it will happen more so on slow cornering but will quickly get louder over a matter of days.
Check the pads for thickness, should be min 6mm

You need to replace the wheel bearing assembly on the drivers side.

It could be a number of things. First check your brakes for any rocks or excessive dirt. Second, check to make sure you are not in need of new brake pads. Brake pads are equipped with a tab that starts making noise when its time to replace your brakes. Third, have the bearing checked. Once the bearing get excessively worn they will start making a squeaky sound. Also have the shocks checked. the bushing worn out in shocks can also cause the noise. The best bet is to have your local mechanic inspect your front end for any wear. Once he does this, he can compile a list of parts that need replaced. Then you can replace or fix it yourself.