"Metal spikes" refers to sharp, pointed objects made of metal. They are often used as a form of protection or for creating traction on surfaces like shoes, tires, or sports equipment. Full definition
This work had a room with one wall made of metal spikes set in a circle. (hammer.ucla.edu)
Kind of the old argument that perhaps cars would be safer if instead of seat belts all cars had a six inch metal spike sticking out of the steering wheel. (sbnation.com)
Depending on which way the bolts fit best, you may now have two metal spikes pointing at your chest when costume is on. (epolitics.com)