for the metal closure on the envelopes.....

Just tear it off and save yourself 20 cents, folks!

but " i use bubble mailers you mean they are suppose to have metal clip?

what metal clip: i dont understand 

Manilla envelopes have the metal clasps on the flap.  Some PO's ask customers to tape over them so they do not 'catch' in the sorting equipment.  Sounds like the OP may have paid a surcharge of some type?

Here are the "rules"

Nonmachinable Criteria

A letter-size piece is nonmachinable (see 6.4) if it has one or more of the following characteristics (see 601.1.4 to determine the length, height, top, and bottom of a mailpiece):

a.Has an aspect ratio (length divided by height) of less than 1.3 or more than 2.5.

b.Is polybagged, polywrapped, enclosed in any plastic material, or has an exterior surface made of a material that is not paper. Windows in envelopes made of paper do not make mailpieces nonmachinable. Attachments allowable under applicable eligibility standards do not make mailpieces nonmachinable.

c.Has clasps, strings, buttons, or similar closure devices.

d.Contains items such as pens, pencils, keys, or coins that cause the thickness of the mailpiece to be uneven; or loose keys or coins or similar objects not affixed to the contents within the mailpiece. Loose items may cause a letter to be nonmailable when mailed in paper envelopes; (see601.2.3, Odd-Shaped Items in Paper Envelopes).

e.Is too rigid (does not bend easily when subjected to a transport belt tension of 40 pounds around an 11-inch diameter turn).

f.For pieces more than 4-1/4 inches high or 6 inches long, the thickness is less than 0.009 inch.

g.Has a delivery address parallel to the shorter dimension of the mailpiece.

h.Is a self-mailer that is not prepared according to 201.3.14.i.

Is a booklet that is not prepared according to 201.3.15.

We were told that even if there was tape over the clasp it was still non machinable as one of the "rules" states if it HAS a clasp..etc etc. If you tape over it, it still HAS a clasp.

So...is there a surcharge for non-machinable mail?

yeah, 20 cents just like the OP said

this surcharge is only for letters. large envelopes(magazine size) and parcels aren't subjected to the surcharge. 

Goodness! I hope all the members to whom I've sent over the years haven't had to pay a charge on their end. I never received notice if they did! When I use a manilla envelope with a clasp. I first run tape along the outside seam long enough to overlap more than enough inside to cover the clasp. So the clasp is never used in any way, just taped over so that it can't be used. That has always been my undertsanding from the PO here. It, the envelope, can be sent as first class if the clasp isn't used.

It can be sent as first class even if the clasp is used. The surcharge is only for LETTERS. it does not apply to things sent as a package. If the clasp is on an envelope sent letter rate, the surcharge applies. 

My post office told me to tape over the clasp on the manila envelopes or they have to charge me extra for not being able to go through the sorting machine.  I just tape the clasp down with packing tape.  It might have started with a mailing that wasn't a book, but I now do it on all my manila envelopes just in case.

I never even use the clasp, just the glue part with tape to reinforce it.