Even if the Seahawks had the cap space to pay Burns's remaining salary this season, which they don't, they would be taking on $11.5M of dead money this year and another $23M of dead money on next year's cap to let Metcalf play cheap for the Panthers, and all so the Seahawks could get a half-season rental of a reasonably good OLB, at a rental price of $16,012,000/18 per week, or $889,555 per week (that'd be over $9M if Burns were to come to the Seahawks next week).
So even if the cap space were there, would a half-season of Burns be worth close to $45M of cap space (split between two years) and letting Metcalf go and play really cheap for somebody else for a season and a half and be available for a reasonable price for the final season of his contract in 2025?