Rule with an
iron fist (heavy handed [no pun intended], dictatorial)
Have an
iron constitution (extremely healthy)
Have an
iron will (very strong-minded)

Balls of
steel or
Brass balls (very stubborn, generally only used to describe men ['balls' being vulgar term for testicles], occasionally for very strong-willed women)
Get down to
brass tacks (get down to business)
Born with a
silver spoon in your mouth (to be born into a wealthy family, to be very lucky/fortunate)
Nerves of
steel (very difficult to disturb or bother)
Buns of
steel (or "abs [meaning abdominal muscles] of steel" - someone who has extremely well-defined muscles esp. in butt)
Steel yourself (prepare yourself for bad news - don't flinch)
Have a
heart of stone (very cold, no compassion)
Strike while the
iron is hot (take advantage of an opportunity)
To have too many
irons in the fire (to have too much going on at once)

Someone that hasn't got a
pot (metal pan) to piss in or a window to throw it out of (someone who has very few belongings)
Mise à jour OK