Oil lamp on and loud rattle

Sounds like the engine bearings are damaged. If the oil level is low, that is the cause of the problem. If the level is okay, it is hard to say which came first. Worn bearings will cause low oil pressure, and that usually gets gradually worse over many miles. Low oil pressure will cause worn bearings, and once that starts to take place, the wear accelerates very quickly. The bearing wear causes the loud knocking in the engine.

Regardless of which came first, low oil pressure results in insufficient oil being sprayed onto the cylinder walls to lubricate the pistons. That results in loss of power and usually overheating. If the engine is stopped right away, many of its internal parts can often be saved. When people try to force it to keep running, more and more parts become damaged from lack of oil, then a total rebuild becomes more expensive, and a used engine from a salvage yard becomes a better deal.

I did not say it did those things. I said, "if... " I can only go by the little information I have.

There are timing chain guides that could be broken, allowing the chain to rattle against the housing. That will make noise, but it will not cause a loss of oil pressure unless the hydraulic tensioner came apart. That would not be common.

A failed oil pump could cause loss of oil pressure, but you would have seen the warning light before damage to the bearings would have occurred. If the warning light came on after the noise started, that suggests the bearings deteriorated, and that caused the low oil pressure. The loss of power also suggests the problem was advancing before the oil pressure dropped and the light turned on.