A metalic noise related to the break pad comes from front right wheel. Two months ago, I changed both the front wheels break pads and the noise started from last month. why it is happening? what is the solution?

Question, you replaced tire on same rim? did you torque to specs? possible over tightened, possible coincidence and brakes are metal to metal.

The brake lining's have worn away, the squealing was metal to metal (worn pad against metal disc) The worn pad will have damaged the brake disc. Very dangerous. You will now have to have new brake pads and discs fitted to BOTH front wheels to put it right. Good luck

wow first post ever for country, im GOBSMACKED !!!!
wheel ?steering wheel or tire/wheel.?

hard to find, they are, all squeaks.
first is to see if possible to do, no moving (big safety issue, yes)
bounce the corners of car hard, by hand.?
jack car up spin tires. by hand,
lever them below off ground, to see of balls are shot.
inspections here, look at every inch of suspenson and parts.

Brakes, i hope nothing breaks the brakes.
The brakes all squeak this is normal try lightly pressing the brake pedal, gently while moving slow, squeaking now is 100% normal and harmless. (the pads act like Guitar strings)
Use pad glue to halt it, or ignore it like me....
the pads have wear markers, they have this device that makes noise when pads get too thin, (look at em)
bad wheel bearings.
brake backing plate bent.
caliper guide pins rusted.
and lots of other things bad or just ok , old and making noise, like
suspension "A" arm bushing rusty, or stable bar , same.

moving noise is real hard to find.

first, check your brake pads, the grinding starts when the pad is worn to the rivets that hold it, then the pad starts to crack and break away. once the pad is gone there will be play that allows whats left of the pad to move around.. causing the thump, there should also be some change under braking, like going from a thump to a grind

this could also be wheel bearings.. but my guess would be the pads, and if it got to that point.. i would bet that the rotor is shot as well

Without hearing it i honestly couldnt say they could all be right and everything is worn out ,have you checked the brake pads for wear in case that is causing the noise like a worn brake disk (rotor) and as the pad wears down the metal on the pad backing is rubbing on the edge of the worn brake disk ?? take the wheel off and have a good look yourself

Drive Axles Joints or Wheel Bearings,a possible cause.

If you Failed to Tighten Any 1 of the Caliper Floater BOLTS and it Has Fallen Out This Will Cause the Noise you Discribe. Remove the Wheel from the SIDE YOU SUSPECT the NOISE is Coming From and INSPECT the Caliper and Pads, If the Bolts ARE there and Tight Check the Brake PADS and If they are Worn DOWN to Metal The Problem Is LIKEKY the Caliper Has SIEZED UP and Needs REPLACED along With Brake PADS and ROTOR.

Most likely the brake shoe in that wheel is worn down to the rivets and those metal rivets are scraping on the drum. If you have a new brake shoe installed right away you will be ok. if you wait, you may also have to have the drums turned. By the way brake shoes come in pairs so they will change both front brake pads. Joe

It sounds like the rear calipers are bad. Raise the rear wheels and see if you can turn the tires. If you can't, open the bleeder. If you still can't replace the caliper. If you can turn the wheel after you open the bleeder, replace the brake hose to that wheel.

You could be right with the wheel bearings. But first take the wheel off and check that nothing is scraping the rotor. Look all the way around the rotor. A suggestion will be that the brake pads have worn enough that the brake pad wear indicator is starting to scrape. Pry them back a little.