I/O Shield won't slot in properly

BoffinBoy125

Honorable
Jan 5, 2014
14
0
10,510
My motherboard will not slot into the I/O shield properly, Also on the keyboard plug on the motherboard there is a metal like arch sticking of. I don't know what this is or what it does but i think its stopping the my motherboard from going in. What should i do?
Thanks.