The phrase 'form a shield' is correct and usable in written English.
It can be used to describe a situation in which something or someone is being protected. For example, "The soldiers formed a shield around their commanding officer."
In the video Rayas showed me, Perzábal is limping badly, and when the judiciales realize that they are being filmed they form a shield around him.
Lear, I decided, surrounds himself with a retinue of 100 knights in order to form a shield of masculinity around himself.
With those images, his team was able to chart precisely how those nine threadlike contrails fanned out over five hours to form a shield of cirrus clouds covering 24,000 square miles.
Crawford said the software and drones, which would be operated by rangers or local law enforcement, would "generate a strategic deployment of rangers in the most cost effective way, so they can form a shield between animals and poachers".
Our 8-year-old, Thor, cowers beneath us - his parents, Astor and Speedie, and me, a surrogate brother, sister, wannabe parent - as we form a shield between him and the miniature cubes pounding down on us.
By legend, this remote valley nestled between the Arabian Sea and the black, crumpled mountains that form a shield against the vast deserts of Arabia is the land of the Queen of Sheba and the place fabled for the gold and frankincense and myrrh that the Wise Men carried to the manger where Jesus was born.
To counter this, Philippicus ordered the men of the central division to dismount and form a shield-wall with their lances projecting from it (the fulcum formation).
The stream, known as the solar wind, is typically deflected by the ionosphere, a layer of ions and electrons forming a shield around Mars.
Finally Michael showed up and made his way through the crowd with about five bodyguards forming a shield around him.
The English formed a shield wall, with the front ranks holding their shields close together or even overlapping to provide protection from attack.
The Bavarian Horse Grenadiers and the Electoral Guards withdrew and formed a shield about Villeroi and the Elector but were scattered by Lumley's cavalry.
