Ppossibly, but can't tell until head and sump come off. Petrol or diesel?
I take it there is nothing obvious like a conrod sticking out the side of the block?
On the other hand, it could be a simple electrical failure - can the engine be turned by hand? If it can't be turned by hand, it is probably serious and expensive, if it can, probably not. (Could not crank over for some people means starter would not turn it, for others means crank handle wouldn't)
The rattle may have nothing to do with the stoppage, but then it may.
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