Glazing bead

[Jeff Eastman]

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[Jerry Peck]

The glazing bead is to hold the window pane in place

Not those vinyl or aluminum ones, they are just decorative. The glazing is held in place by the sealant.

[Rick Hurst]

That plastic trim in your picture looks like its been beat to hell with hail.

Those chipped areas as is present on the side is a giveaway. Always a clue to check out the roof really well.

As JP said, there should be sealant around the glass panel which would keep the moisture out.

Looks like the window has a lost thermal seal anyway, so it needs to be replaced.