In the 1940s, it was usual for Hollywood Studios to issue a publication towards the end of each year to show cinema owners what they could expect in the following year.
MGM went one better and produced The Lion’s Roar magazine every two months (sometimes monthly) for exhibitors and studio employees.
Supervised by Howard Dietz, head of publicity, it had at least 100 pages (11”x 14”), with color cover Art and often color pictures inside.
The artist Jacques Kapralik often did the covers.
There were 32 issues and three supplements. One sold on EBay for $140.
Does anyone own one? They are pretty rare.
Regular publication was discontinued in 1947.
Inside pages of the MGM 20th Anniversary issue.
Van Johnson.
A feature on Madame Curie.
Undercurrent, with Katharine Hepburn, Robert Taylor.
This was labelled as Lucille Ball in ZIEGFELD FOLLIES.
A collection of MGM players serving in the forces.
William Powell, Hedy Lamarr.
BOOM TOWN.
A WEEKEND AT THE WALDORF.
Inside color splash for BATHING BEAUTY.
Vienna's Classic Hollywood 
I have 29 images on my Pinterest page. Wonder which ones I’m missing. https://www.pinterest.co.uk/siriami/lions-roar-covers/
I remember seeing your covers. Thanks for link.they look great.
What interests me about this more than the publication itself, is that it was “supervised” (edited?) by Howard Dietz. Far more than a publicist for Mayer, he was also a great Broadway lyricist with composer Arthur Schwartz. His memoirs, “Dancing in the Dark”, after one of his classic songs, is a unique testament to him – written simply (even humbly) with the sophistication and literacy of a bygone age; yet plenty of vaudeville “kick”, too! A wonderful read, totally alive. Published in ’74…
Indeed, I love his songs. The Band Wagon is my favourite musical.
What a talent he was. Will try and get his book, thanks for the information.
My favorite movie musical, too! Thank you for replying. The book, with fascinating preface by Alan Jay Lerner, is worthwhile and a delight.