I never plan meetings with external partners on Mondays. It actually goes back to the time when I was running my dinner kit business (link), but I have kept the habit. Don’t let anyone or anything derail you on Mondays – keep you mind and time free to plan your week.
If you have employees – I strongly recommend meeting on Monday morning/before lunch.
On Sunday: think what you want to achive, think how.
On Monday: communicate to your team. Ask how to achieve it! Agree on a actions for the week.