You don't say whether your car is petrol or diesel.   Mine is a 406 2.0L HDI
110 and developed a rattle most noticeable as the engine slowed down after
blipping the throttle.   Last weekend when my son-in-law and I were
investigating we removed the large flat cover on top of the engine to see
more clearly and the noise disappeared.   The car is now running sans cover.

the banging noise from the front is probly anti roll bar rubbers,mine on
my 405 are banging about .i am waiting for warmer weather to come before
i get under mine to do the jobs so it hang on till then.the rattle noise
is probly the oil not on the cam, when was the oil changed?

The banging noise when you're driving may be anti roll bar drop links, it
will be obvious because it will happen when you drive on a rough surface;
these are a common fault on the 406. Dead cheap if you buy them from GFS but
a pain to remove if they're the originals because you have to insert a Torx
bit into the end to hold them whilst you unbolt the nut and frequently the
hole rounds out so you have to cut them off; if they've been replaced before
you may find that they have 2 flats on the joint side of the attachment
point so you can counter-hold them with a (thin) spanner, in this case they
can be changed in a few minutes.
Martin