They probably would have trouble moving.
Lets assume a few things - if this is a surface transformation, their muscles would need to adapt to a heavier 'skin' without the stretchiness of human skin. They'd have to overcome weight and friction of their skin plates, or have a surface coating that is barely at the liquid/metal transition phase.
If its the latter, basically anything hot enough would just pierce through.
If muscles were transformed as well, they'd have to instantaneously change to another mechanism and physical material. The closest thing to muscles is memory metal and that's complicated, not very efficient, and relies on a different mechanism from muscles - heat rather than power.
Also, having your lungs turn to metal would deprive you of oxygen and you'd die, assuming your brains didn't turn to metal as well. I have no idea how having a steel brain would work.
So. Not very strong at all, but you'd make a lovely statue for pigeons to roost.