Hearing a strong sound when hitting a curb I bought a  hardtail MTB about a month ago (a complete beginner) and the way I'm dealing with curbs is:


I'm going at a decent speed
I slightly lift my front wheel
I shift my weight off the back wheel (it's 27.5" and i have it on near maximum pressure 
) and it hit the curb (and I hear a strong sound - sort of metal hitting concrete)


I had my friend to check if anything was touching the ground, he said nothing but the wheel.

Is this the right way to do it? Do I need to put more pressure to the wheels?
Thanks for your time, I really appreciate it.
The technique is correct, ideally you are lifting the front followed by the back wheel so they clear the curb (the back wheel brushing the curb lightly is OK). This is known as a J-Hop or American Bunny hop.  The technique does take practice as the timing has to be accurate, looks of videos online that teach how to do it in sequences. The English Bunny hop is an alternate way - simple lift both wheels off the ground at the same time and land at the same time -  with enough speed you clear the curb. Both techniques are valid and have their place.  

Often the noise comes from the the chain hitting the chain stay. If you are are on small cogs, its more likely to happen (more slack in the chain and close to the chain stay), if you have a clutch derailleur (and the clutch is engaged), it is less likely to happen.