Or change to a D1 Mini pro with an external antenna (just don’t forget to move the zero ohm resistor).
Pete.
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I got it ! Thank you !! 
You can try that
He wasn’t kidding when he said he want an expert!
The problem is that with a metal box you really need screened (coax) cable between the board and the outside of the box, then a well designed antenna that’s going to be waterproof. Like this:
Pete.
Yes but, you can solder a coax cable too 
That antenna will work better if the ground connection is in contact with the metal box, the box will act as a ground plane then.
But, if you’re going to drill a hole in the box to mount the antenna then pit it on one of the sides or the bottom to stop water getting in when it rains.
Pete.
I use the antenna as the picture . Do you mean that I can use the SMA to lock on the box ? I have drilled a hole on the side of the box ! I use it indoor so there is no water problem.
Yes, there should be some locknuts and washers with the antenna. Drill a hole and pass the brass bit through it then put the locknut and antenna on. Make sure you clean-up the area around the hold so that the brass part gets good electrical contact with the box.
Pete.
Thank you , sir . I will try it.