toyota corolla
 

i own a 1996 toyota corolla. Last evening when i was driving on the
interstate i heard a rattling sound from my engine. I pulled over. I
saw very little smoke coming from around a bolt on the engine head
cover which was covered with oil. The sound was coming from the left
side of the engine block when the engine is viewed from front.

The engine did not get over heated and the oil lights did not light up.
The engine still starts but it makes this hel lot of a rattling noise.

What could be the problem? Am i looking at something very serious.