1968's Hand Catching Lead was Serra's first film (youtube will try and tell you it was made in 1971, but that's youtube). Serra claims it was an attempt to break into the "intimidating" medium of film, inspired by the "great freedom" he saw expressed in Warhol's work and the "tentative, experimental" nature of films like Yvonne Rainer's Hand Movie and Line.
He was originally asked to document the making of his sculpture, House of Cards, in which huge sheets of lead are balanced against one another, held up by their own weight, but decied that a traditional documentary would not be able to capture the creative process. Instead, the work is a "filmic analogy" of the construction of the sculpture: his catching of the pieces of lead is a more refined representation of months spent lugging blocks of lead around his attic with Philip Glass.
Hand Catching Lead has been described as a "non-event" by critics. The single, continuous, soundless shot of a hand catching and immediately dropping pieces of lead is almost hypnotically repetitive but has no sense of purpose or urgency. The film is not building to any kind of climax, nothing we see is explained and there is no attempt to create the impression of a seamless 'performance' which isolates the images from the world around them (in the second half of the film, another hand is visible collecting and dropping the lead, while the hand hurries it along). Part of this can be explained by the fact that the film is supposed to be a recreation of Serra's creative processes, which he describes in very abstract terms:
If I define a work and sum it up within the boundary of a definition, given
my intentions, that seems to be a limitation on me and an imposition on other
people of how to think about the work. Finally, it has nothing to do with my
activity or art. I think the significance of the work is in its effort, not in
its intentions. And that effort is a state of mind, an activity, an interaction
with the world... The focus of art for me is the experience of living through
the pieces, and that experience may have very little to do with the physical
facts.