Have a sudden issue at my house. Turned on a light and a spark and audible bang resulted from the stem where the light bulb attaches. 10A fuse on the switchboard blows.

I reset switch and try again - boom! Same thing with a visible spark and audible bang. Light bulb worked momentarily and isn't blown.

I switch the light bulb and boom! Same thing. At this stage I give up and will call for electrical help.

Any ideas on likely problem? Hoping it won't be expensive.